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DREDGING  FOR  GOLD 
IN  CALIFORNIA 


BY 

D'ARCY   WEATHERBE 

Member  of  the  Canadian  Society  of 
Civil  Engineers 


FIRST  EDITION 


San  Francisco 

MINING  AND  SCIENTIFIC  PRESS 
1907 


o0' 


REESE 


COPYRIGHT  1907 

BY 

MINING  AND  SCIENTIFIC  PRESS 


AUTHOR'S    ACKNOWLEDGMENT. 

In  completing  the  following  work  I  wish  to  acknowledge  the 
courtesy  shown  to  me  and  the  efforts  that  were  made  to  facilitate 
my  examinations  among  the  dredging  districts  of  the  Sacramento 
valley,  also  for  many  valuable  suggestions  and  data  that  have  been 
furnished  to  me.  Special  acknowledgment  is  due  to  W.  P.  Ham- 
mon,  George  L.  Holmes,  W..  S.  and  B.  Noyes,  Charles  Helman, 
Newton  Cleaveland,  R.  G.  and  Albert  Hanford,  John  Plant,  Karl 
Krug,  O.  W.  Jasper,  J.  H.  Leggett,  H.  Appel,  F.  J.  Estep,  and  to 
many  others. 

SAN  FRANCISCO,  October  6,  1906. 

D'ARCY  WEATHERBE. 


EDITOR'S    NOTE. 

Owing  to  his  absence  in  South  America,  the  author  has  been 
unable  to  read  the  proofs  of  this  book.  It  has  been  my  pleasant  task 
to  edit  Mr.  Weatherbe's  manuscript,  knowing  how  careful  he  has 
been  in  collecting  the  data  on  which  this  treatise  is  based;  it  is  the 
result  of  judicious  investigation  by  a  trained  engineer  and  it  will 
commend  itself  to  the  profession. 

T.  A.  RICKARD. 

SAN  FRANCISCO,  April  22,  1907. 


161471 


TABLE    OF    CONTENTS. 

Page 

Author's    Acknowledgment       ....        .  .        <      '..        .           1 

Editor's   Note           .        .        .        ...        .  ...              1 

I.     Introductory        .        . '     /  .        .        .        .        .  .        ,        .          9 

II.     Prospecting     Dredging     Ground       .        .        .  .        .        .        .        27 

III.  Dredging    Machines        .               ".        ...  ...            46 

IV.  Operation     ./.;-.      ....        .        .     •  .        .  .        .    *    .        .        88 

V.     The   Metallurgy  of  Dredging       .         .        .        .  .        .        .          109 

VI.     Costs    .    *    .        .        .   .  II  £    .        .."> '"  ...  '    .,  .        .        ...     139 

VII.     The    Horticultural    Question        .        ....        .        .  164 

VIII.     General         .        .        .        .        .        .        .        .  .        .        .        .       170 

IX.     Appendix          ...        .     "   . 

Contribution  by  J.  H.  Curie       .        .        .  .                 .        .       183 

Gold  Dredging,  Editorial       .        .        .        *  ,        .        .          188 

Sectional   Dredging   Machinery,   Editorial  .        ..        .        .       190 

Contribution  by  G.  L.  Holmes       .        .        .  .        ^        .           192 

Contribution  by  C.  W.  Purington     .         .  .        .        .        .       194 

Contribution  by  D'Arcy  Weatherbe       .        .  .        .        .          200 

Contribution  by  D'Arcy  Weatherbe          .  .        .        .        v      206 

Cost   of   Dredging,    Note       .        .        .        .  .        •.      '  .    •      209 

Contribution  by  C.  W.  Purington      .        .  .        .                 .      210 

Index  215 


LIST    OF    ILLUSTRATIONS. 

Fig.  Page 

A  Modern  Dredge  in  Operation       .    '     ..        .         Frontispiece 

1.  Map    Showing   the    Principal    Dredging    Districts     .         .        V  H 

2.  The  Valley  of  the  Feather  River       .       .        -.                  .         .  12 

3.  Hull  of  Dredge  in  Course  of  Construction        ..'.'.         .  13 

4.  Bed    of    Gold-bearing    Gravel    at    Mississippi    Bar         .         .  17 

5.  Road-Cutting   near   Folsom           .    .     .'        .         .         .         .         .  19 

6.  Spill-Way  of  the  Barrier  Dam  on  the  Upper  Yuba       .   •"•    .  21 

7.  The   Barrier  Dam   on   the   Yuba         .         .         .         .         .       : .  23 

8.  Upper  Feather  River         .       .         ."'..:        .         .      '   .         .  24 

9.  Marysville    Rapid    Transit          .......         .         .  25 

10.  Bringing    a    Keystone    Driller    into    Place         ,         .    .     .         .  29 

11.  Prospecting  Drill  and  Recovery  Process  on  the  Yuba         .  31 

12.  Rocker  and  Second  Settling  Vat        .         .         .         .         .         .  35 

13.  Delivery- Vat,    First    Settling- Vat,    and    Sand-Pump         .         .  37 

14.  Garden  Ranch  Dredge,  Oroville       .         .         ...                  '.  47 
14^2. Diagram  Illustrating  the  Development  of  the  Dredge        .         .  48 

15.  Garden  Ranch  Dredge.     Dipper  in  Action     .    '     .         ...  49 

16.  Garden  Ranch  Dredge.     Crane,  Showing  Gearing  from  Rear  50 

17.  Exploration  No.  3  Dredge  Being  Built  on  the  Bank      ...  51 

18.  Frame  of  No.  3  Dredge,  Folsom         .         .         .         ...  53 

19.  A-Shaped    Forward    Gauntree    on    the    Ophir         .  '               .  55 

20.  Risdon  Dredge  at  Fair  Oaks         .         .                  .                  .    .     .  56 

21.  Forward  Gauntree  on  Boston  No.  4         ...         .         .  57 

22.  Lattice-Truss   Digging-Ladder   of   Yuba    No.   8         .         .         .  58 

23.  Digging-Ladder  and  Buckets  on  Oroville  Dredge         .  59 

24.  Rollers  on  Digging-Ladder,  No.  3  Folsom         .         .     •    .         .  60 

25.  Lower  Tumbler  of  Folsom  No.  4,  Showing  Wearing  Plate  61 

26.  Lower  Tumbler  Casting   of   Digging-Ladder     .         ,         ...  62 

27.  Lower  Tumbler  on    the    Ophir         .         .         ..        .         .         .  '  63 

28.  Close-Connected  Bucket-Line  on  the  Butte        .'.'•.'-•    -"'".•         •  64 

29.  Open-Connected  Bucket-Line  on  the  Baggette        ...  65 

30.  Repairing    Lower    Tumbler    of    Exploration    No.    2         w         .  67 

31.  Bucket  of  13  Cubic  Feet  Capacity,  on  Folsom  No.  4        .  68 

32.  Bucket-Emptying   Jets    on    the    Butte         .         .         .         .         .  69 

33.  Stacker-Discharge  on  Folsom  No.  4       .       ~.         .    c'    .    .-    .  70 

34.  Belt-Conveyor  on   Exploration   No.   2         .         .         .         '.         .  71 

35.  Belt-Conveyor  Stacker  on  Folsom  No.  4        .      '  .        .         .  72 

36.  Belt-Conveyor  on  Folsom  No.  3           .         .      .  .         .  -'•    .         .  75 

37.  Feather  River  Exploration  No.  1,  Showing  Pan-Stacker       .  77 

38.  Motors  and  Ladder-Hoist  Winch  on  Boston  &  California  No.  3  79 


6  LIST  OF  ILL USTRA  TIONS. 

Fig.  Page 

39.  Sprocket-Gear  Driving  Arrangement  on   the   Pennsylvania  80 

40.  Pentagonal   Equalizing  Gear         .......  81 

41.  Folsom   No.  3,   Showing  Standard  Type   of   Drive-Gearing  82 

42.  Wooden  Spud  of  the  Ophir 83 

43.  Broken  Steel  Spud,  Yuba   No.    1 85 

44.  Well  of  Yuba  No.  8,  Showing  Tumbler,  Grizzly,  and  Sluices  87 

45.  Method  of  Anchoring  and  Moving  the  Boat         ...  88 
45^. Cross-Section  of  Steel  Spud 89 

46.  Method  of  Anchoring  a  'Dead-Man' 90 

47.  Appearance  of  Bank  when  Spuds  are  Used      ....  90 

48.  Appearance  of  Bank  when  Head-Line  is  Used      ...  90 

49.  Chinaman   Removing  Trees  in   Front  of    a    Dredge         .         .  91 

50.  Removing  Stumps  Along  Irrigation  Ditch       ....  92 

51.  Movement  of  Boat  by  Side-Line 93 

52.  Working  Against  Right-of-Way  Stream         ....  94 

53.  Tail  Sluices  and  Spuds  on  Yuba  No.  7         .....  95 

54.  Folsom  No.  5.     Working  High  Bank  with  Water  Jet         .  97 

55.  Sand  Pump  Working  on  Yuba  No.  7 98 

56.  Plan  Showing  Cuts  Across  Pit,  and  Prospective  Cuts         .  100 
56J/2. Daily  Report  of  Dredging  Department       .                   ...  101 

57.  Bucket-Line  Laid  Out  on  Shore  Ready  for  Yuba  No.  8        .  103 

58.  Accident   to    Bucket-Line    on    Yuba    No.   2         ....  104 

59.  Cable  Transport  by  Board  Trestles 105 

60.  Cable  Transport  by  Barrel   Pontoons 106 

61.  Cable  Transport  by  Forward    Gauntree          ....  107 

62.  Tail  Sluice,  Showing  Angle-Iron  Riffles  and  Cocoa  Matting  110 

63.  Trommel,  Stacker,  Tables,  and  Sluice  on  Exploration  No.   1  111 

64.  Clean-up  Apoaratus  and  Riffles  on   the  Butte         .         .         .  112 

65.  Revolving  Screen,  and  Tables   on  the   Yuba   No.  4         .         .  113 

66.  Tables   on   the   Pennsylvania     .......  115 

67.  Riffle  Tables  and  Stream-Down  Box  on  Bibbs  No.  2         .         .116 

68.  Screen,  Sluices,  and  Tables  on  Leggett  No.  3         .         .         .  117 

69.  Screen,  Table,  Launders,  and  Sluices   (Holmes)   on   El   Oro  119 

70.  Screen  and  Tables  on  the  Baggette 120 

71.  Launder  Delivery  and  Lower  Tables  on  the  Baggette        .        .  121 

72.  Tail    Sluice    on    the    Baggette 121 

73.  Sluice,  Plate,  Screen  on  Folsom  No.  4        .....  122 

74.  Screens  and  Tables  on  Folsom  No.  5 123 

75.  Stacker  and   Remodeled   Sluices   on   Folsom   No.  4        .         .  125 

76.  Trommel   on   Yuba   No.   8 129 

77.  Long  Tom   on   Yuba   No.   4        .......  131 

78.  Clean-Up   Apparatus   on   Butte   and    El    Oro         .         .         .  133 

79.  Jets  for  Shaking  Screen,  on  the  Garden  Ranch-  Dredge         .  135 

80.  7y2  Cubic  Feet  Bucket  on  Boston  No.  4        .         .         .         .  139 

81.  Same  as  Fig.  80,  but  Rear  View        .  140 


LIST  OF  ILLUSTRATIONS.  7 

Fig.  Page 

82.  Upper  Tumbler  of  El  Oro  No.  1,  Stripped  of  Wearing  Plates  146 

83.  Lower  Tumbler,  Showing  Wearing  of  Cushion  Plates         .  147 

84.  Bucket  Line  of  the  Ashburton  Dredge       .         .        '.         .  .  148 

85.  Idler  Drum.     Diameter  9  feet  6^  inches         ....'.  149 

86.  Showing  Wear  of  Bucket  Bottom  and  Pin       ..         .         ..  .  150 

87.  Bucket  Line,  Showing  Wear  of  Lips       .         .         .         .         .'  151 

88.  Wear  Plates  for  Lower  Tumbler         .         .         .         .•      .  .  153 

89.  Wear  Plates  with   Lugs  for  Upper  Tumbler         .         .         .  153 

90.  Ladder   Hoist   on   the   Bagerette          ..        .        .   •     .       ','.'  .  156 

91.  Showing  Wear  on   Lips  of  El  Oro   Buckets         .        .        .  157 

92.  Belt-Conveyor  on  Stacker-Ladder  of  Folsom  No.  3        .  .  163 

93.  Eucalyptus  Two  Years  After  Being  Planted  on  a  Sta.-k  Pile  166 

94.  Eucalyptus  Just   Planted  on   Stack   Pile         .        .        ..         .  167 

95.  Flat  Tailing   Bed   of  an   Old   Dredge         .         .         .         .  .  169 

96.  Remains  of  Old  Workings  on  the  American  River         .         .  171 

97.  Old  Chinese  Workings  at  Folsom       ...         .        .  .  172 

98.  Gravel    Bank    at    Oroville         .         .   .     .        .        .    '     .     .    .  173 

99.  An   Old   Miner  and   His    Rocker        .         ......  .  174 

100.  Sketch    Map    of    the    Yuba    Bottom         ,         .         .'      .      •  .  179 

101.  The    Treacherous    Yuba    Bottom        ,         .       «...        .  .  181 
101  ^.Middle  Fork  of  American  River       .        .         .        ;        .        .  182 

102.  Wreck  of  the  Colorado-Pacific      .         .        .        .        .         .  .190 

103.  Feather  River,  with  Dredges  in  Operation       .                 .         .  213 


I.    INTRODUCTORY. 

Gold  dredging  has  won  an  important  place  in  the  industry  of 
mining,  and  it  has  done  so  by  right  of  hard-earned  merit.  Prob- 
ably no  branch  of  mining  has  come  so  prominently  to  the  front  in 
so  short  a  time ;  by  proving  its  commercial  value  it  has  opened  to 
the  financier  an  opportunity  for  safe  and  large  investments. 

Ten  years  ago  there  were  no  dredges  working  in  California. 
Today  there  are  fifty,  either  in  operation  or  building  in  the  districts 
of  Oroville,  Yuba,  and  Folsom,  and  it  is  probable  that  in  no  single 
instance  is  money  being  lost,  while  many  of  the  dredges  are  clear- 
ing net  profits  of  from  $2000  to  $5000  per  month. 

It  is  estimated  that  over  $5,000,000  is  invested  in  the  business 
of  dredging  in  the  three  districts  of  Oroville,  Yuba,  and  Folsom,  an- 1 
the  combined  producing  capacity  in  these  three  districts  is  estimated 
at  an  annual  output  of  about  30,000,000  cubic  yards. 

Naturally  in  such  a  young  and  growing  field  there  is  tre- 
mendous diversity  of  opinion  as  to  the  relative  advantage  and  value 
of  the  different  methods  in  the  practice  and  design  of  the  machines 
and  their  parts.  In  the  account  presented  herewith  I  have  endeavored 
to  trace  the  progress  of  the  industry  in  California,  and  to  give  as 
many  actual  examples  from  practical  experience  as  possible. 

Geological  and  Historical. 

The  explorations  of  the  United  States  Geological  Survey  have; 
defined  three  great  mineral  belts  in  California.  Three  parallel  lines 
are  to  be  observed  in  the  structure  of  the  region;  the  first  is  coin- 
cident with  the  summit  of  the  Sierras,  the  second  is  along  their 
approximate  base,  say,  from  Visalia  to  Red  Bluff  and  about  fifty 
miles  west  of  the  first  or  main  axial  line,  and  the  third,  equidistant, 
drawn  from  the  neighborhood  of  Clear  lake  to  Kern  lake,  marks 
the  eastern  edge  of  the  Coast  Range,  the  shores  of  the  Pacific  form- 
ing its  western  edge  at  about  the  same  distance.  These  lines 
divide  the  State  geologically  as  well  as  physically.  The  Sierra 
Nevada  is  a  belt  of  intrusive  granite  of  ante-Cretaceous  elevation, 
but  of  Triassic  and  Jurassic  age,  partially  covered  by  important 


10  DREDGING   FOR   GOLD   IN  CALIFORNIA. 

Pliocene  river  deposits.  These  mountains  are  of  great  height  and 
are  the  region  of  precious  metal  (and  some  iron  and  copper) 
mining,  while  the  Coast  Range,  formed  of  strata  chiefly  of  Cretaceous 
or  Tertiary  age  and  of  post-Cretaceous  elevation,  yield  principally 
quicksilver  ores  and  carbonaceous  minerals. 

In  the  Sierra  Nevada,  volcanic  activity  is  supposed  to  have 
ceased,  while  solfataric  and  seismic  disturbances  are  still  apparent 
in  the  Coast  Range,  the  effect  of  the  latter  having  been  terribly 
illustrated  in  the  recent  earthquake  and  its  disastrous  consequences. 
The  great  valley  lying  between  them  is  covered  by  recent  alluvial 
deposits  laid  down  on  the  bed  of  a  fresh-water  sea.  It  is  to  a  part  of 
the  western  border  of  this  region  that  attention  is  to  be  drawn.  The 
gravel  deposits  occur  in  every  variety  of  texture  from  fine  pipe-clay 
through  sand  and  gravel  to  rolled  pebbles  and  boulders,  sometimes 
weighing  tons.  It  is  now  generally  accepted  that  they  have  been  laid 
down  by  the  action  of  a  system  of  late  Tertiary  rivers  which  had 
nearly  the  same  general  course  as  the  present  streams  on  the  west 
slope  of  the  Sierra,  but  whose  channels  were  wide  and  slopes 
greater. 

The  waters  of  these  rivers,  eroding  the  auriferous  slates  with 
their  included  quartz  veins,  concentrated  the  precious  metals  in 
deposits  often  350  to  400  ft.  wide  at  the  bottom  and  sometimes 
several  thousand  feet  wide  at  the  top.  Their  depth  now  varies  from 
a  few  yards  up  to  six  or  seven  hundred  feet.  Volcanic  eruptions 
have,  in  places,  covered  these  deposits  with  lava  and  tufa  hundreds 
of  feet  thick.  Denudation  and  erosion  ensued,  and  the  products  of 
volcanic  activity  have  sometimes  been  covered  in  turn  with  gold- 
bearing  detritus. 

Ages  ago,  long  before  the  advent  of  man  upon  this  planet,  the 
western  coast  of  the  continent  lay  approximately  along  the  line  of 
the  present  Sierra  Nevada  range,  then  included  in  flat  beds  of  shale 
and  slate  and  on  a  level  with  the  present  great  interior  plains.  The 
present  buried  river-beds  had  their  origin  in  immense  sluggish 
streams  or  sloughs  of  great  length  and  extremely  tortuous.  These 
probably  included  watersheds  as  far  north  as  the  present  Columbia 
river;  they  extended  east  into  Utah  and  emptied  into  the  ocean. 
Presently,  however,  a  change  occurred  in  affairs  terrestrial  and  an 
uplift  began  to  produce  the  Sierra  Nevada  mountains.  These 
sloughs  with  their  increased  grades  became  roaring  torrents,  erod- 


12 


DREDGING   FOR    GOLD   IN   CALIFORNIA. 


ing  deep  channels  through  the  embryo  mountains  and  tending  to 
straighten  their  sinuosities  in  the  long  and  turbulent  journey  to  the 
sea.  Though  enormous  bodies  of  detritus  must  have  been  washed 
away,  none  of  it  remained  in  the  river-beds  owing  to  the  fierce 
rush  of  the  current.  The  upheaval  which  lifted  the  Sierras  to  an 
altitude  greater  than  even  that  of  the  present  magnificent  peaks, 
abated  and  finally  ceased ;  a  period  of  erosion  commenced.  Up  to 
this  point  it  is  probable  that  the  river's  burden  was  non-auriferous, 
but  from  the  interior  magma  the  slate  and  schist  were  penetrated 
by  intrusive  lava,  followed  by  thermal  activity  that  produced  veins, 


Fig.  2.     The  Valley  of  the  Feather  River. 

the  source  of  the  gold  in  the  placer  mines  of  today.  The  Glacial 
epoch  followed  and  during  the  rainy  period  that  ensued,  with  the 
renewed  influence  of  the  sun's  heat,  tremendous  erosion  occurred; 
the  peaks  were  worn  down,  and  the  ravines  and  valleys  were  formed. 
Simultaneously  another  phenomenon  occurred  that  had  an  all-im- 
portant bearing  on  mining.  The  valley  of  the  Sacramento  river, 
lying  between  the  Sierra  and  the  Coast  Range,  which  had  meanwhile 
become  a  vast  inland  fresh-water  sea,  began  to  rise.  This  uplift  in- 
cluding the  foothill  country  and  its  total  vertical  effect  is  variously 
estimated  at  from  800  to  1000  ft.  The  immediate  result  was  a 
decrease  in  the  grade  of  the  great  river  system  and  the  consequent 
slowing  of  the  current,  the  channels  becoming  gradually  filled  with 


14  DREDGING   FOR   GOLD   IN   CALIFORNIA. 

gravel,  sand,  and  silt,  containing  the  concentrated  gold  from  the 
eroded  portions  of  the  veins  over  which  they  coursed. 

Contemporaneously,  man  appeared,  and  no  written  papyrus  is 
necessary  to  record  the  event.  Certain  it  is  that  he  did  not  exist 
during  the  immediate  post-Glacial  period,  but  at  this  stage,  when 
the  rivers  were  filled  with  gravel,  we  have  abundant  evidence  that 
he  had  even  progressed  in  the  arts.  His  prehistoric  stone  mortars 
for  pulverizing  maize  or  other  cereals  are  constantly  being  brought 
to  light  in  the  hydraulic  and  drift  mines,  and  piles  of  faggots  and  fire 
wood  stacked  by  hand  and  exposed  in  the  bench  workings  of  the 
ancient  rivers  suggest  the  site  of  aboriginal  habitations. 

The  final  destruction,  by  burial,  of  the  life  of  these  channels 
came  about  through  volcanic  activity,  which  was  at  work  only 
periodically  during  a  comparatively  short  geological  period;  up  to 
the  time  of  the  final  outburst  of  molten  lava,  it  appears  to  have  pro- 
duced mainly  ash  and  dust  that  were  swept  down  the  streams  in 
form  of  sand  and  slime.  Subsequently  this  ejected  material  was 
compressed  into  the  various  layers  of  rhyolite  and  other  tufaceous 
rock  of  different  coarseness.  Between  these  there  were  often  beds 
of  alluvium  produced  from  detritus  of  non-volcanic  origin. 

There  seems  only  to  have  been  one  general  flow  of  actual 
melted  lava,  remnants  of  which  may  now  be  seen  in  the  basaltic  cap 
forming  the  isolated  table  mountains  existing  at  several  points  in 
the  foothills,  notably  on  the  Feather  river  and  in  Stanislaus  county. 
This  cap  was 'in  turn  worn  down  by  the  later  rivers,  often  flowing 
in  an  entirely  different  direction  to  the  buried  channels ;  these  are 
thus  found  today  at  varying  elevations  up  to  several  hundred  feet 
above  the  existing  rivers,  which,  cutting  the  ancient  channels  at 
many  points,  are  locally  indebted  to  them,  as  well  as  to  the  quartz 
lodes,  for  their  gold.  Indeed,  it  is  probable  that  to  this  secondary 
concentration  is  due  most  of  the  enrichment  at  those  favorable  spots 
that  provided  the  gold  of  the  pioneers,  and  in  fact  all  of  the  gold 
obtained  in  the  pan,  rocker,  sluice,  and  other  river  workings.  These 
streams  of  later  origin  continually  changed  their  channels,  though 
continuing  to  flow  approximately  in  the  same  direction,  and  at  each 
change  they  cut  deeper.  The  result  was  that  a  series  of  terraces,  bars 
and  benches  were  formed,  gradually  rising  from  the  present 
channel.  A  striking  example  of  this  action  may  be  seen  during 
almost  any  month  in  the  year  in  the  Yuba,  but  more  emphatically 


INTRODUCTORY.  15 

shortly  after  the  winter  rains.  Long  sections  of  the  river  shift 
as  much  as  several  hundred  feet  in  a  few  weeks,  leaving  gravel 
bars  deposited  in  positions  that  a  few  days  before  represented  the 
channel. 

On  the  American  river  half  a  dozen  distinct  benches  may  be 
observed  rising  from  the  south  side  of  the  river  for  several  hundred 
feet  in  height,  and  each  of  these  contain  consecutive  auriferous 
channels — the  former  courses  of  the  present  river.  It  is  these 
later  river  channels  that  in  most  cases  form  the  richest  portions  of 
the  dredging  areas  of  today  in  almost  every  instance,  though  of 
course,  quantities  of  gold-bearing  matter  must  have  been  deposited 
by  the  ancient  rivers  previous  to  their  becoming  choked  by  the 
flow  of  volcanic  material.  That  the  gold  from  this  source  does 
actually  exist  at  greater  depths  than  it  is  possible  to  dredge  (with 
present  apparatus)  has  been  proved  by  several  comparatively 
deep  bore-holes  that  penetrated  below  one  or  more  beds  of  volcanic 
ash  and  also,  I  believe,  by  drift-mining  operations  in  a  few  cases. 
Most  of  these  drift  mines  worked  by  shaft  in  the  valley  are  prob- 
ably on  the  beds  of  the  recent  channels. 

Several  ingenious  theories  have  been  advanced  to  account  for 
the  source  of  the  gold  in  the  channels,  but  in  no  case  has  a  reason- 
able argument  been  put  forth.  The  'marine  idea'  holds  that  these 
beds  were  deposited  on  the  floor  of  a  sea,  but  that  this  is  altogether 
fallacious  is  shown  by  the  fact  that  no  marine  remains,  have  been 
detected  and  terrestrial  signs  such  as  trees  and  even  human  im- 
plements and  (in  some  of  the  older  beds)  remnants  of.  mammals, 
such  as  the  mastodon,  are  found.  The  famous  'blue  lead'  theory 
pre-supposed  the  existence  of  an  ancient  river  flowing  from  north 
to  south  and  roughly  parallel  with  the  crest  of  the  Sierras  (some 
said  this  could  be  traced  from  Alaska  to  Mexico)  and  containing 
a  characteristic  blue  gravel.  In  the  first  place,  it  has  been  proved 
that  no  such  ancient  channel  exists  and,  secondly,  that  the  'blue 
lead'  forms  the  bottom  stratum  of  practically  every  buried  channel, 
of  Pliocene  age,  that  has  been  opened.  By  analysis  the  'blue 
lead'  gravels  contain  iron  pyrite,  and  these  strata  are  similar  in 
every  way  to  the  'red  leads'  or  'rotten  boulder'  leads  as  they 
are  called,  which  generally  overlie  them,  except  that  in  the  latter 
case  the  iron  has  become  decomposed  and  changed  to  an  oxide. 


16  DREDGING   FOR   GOLD   IN  CALIFORNIA. 

That  the  gold  is  evidently  derived  from  the  bedrock  traversed 
by  the  channel  systems  seems  practically  certain.  The  argument 
has  frequently  been  brought  forward  that  the  Veins  throughout 
many  of  these  districts  are  too  poor  to  pay  for  working  even  under 
present  economic  conditions.  This  does  -not  necessarily  justify 
the  conclusion  that  they  were  too  poor  to  furnish  gold  to  the 
channels.  Some  of  the  quartz  veins  have  shown  gold  enough  to 
warrant  the  investment  of  capital  and  they  have  even  paid  a  profit. 
The  $2  to  $5  per  ton  that  the  average  of  these  deposits  contain  is 
an  extremely  fine  concentrate  and  represents  the  product  of  a  small 
fraction  of  the  mass  of  quartz  broken  and  sluiced  down  these  old 
rivers.  Moreover,  some  of  these  veins  have  been  eroded  to 
depths  approximating  1000  ft.  and,  incidentally,  many  fabulously 
rich  pockets  must  have  been  treated  by  nature's  concentrator — the 
river. 

Placer  deposits  have  been  the  earliest  sources  of  gold  through- 
out the  world  and  since  1848,  the  date  of  the  first  important  find 
in  California,  it  is  estimated  that  about  four-fifths  of  the  total 
output  has  been  produced  by  the  different  forms  of  alluvial  mining 
in  this  State.  The  total  production  from  all  sources  up  to  date 
has  been  $1,450,000,000. 

The  successive  steps  in  placer  mining  were  the  miner's  pan, 
the  cradle  or  rocker,  the  long  torn,  the  riffle-box  or  sluice,  the 
ground-slui9e,  booming  or  gouging,  drift  mining,  hydraulic  mining, 
the  hydraulic  elevator,  and  dredging. 

The  pan,  rocker,  and  long  torn  are  almost  too  well  known  to 
mention  and  may  be  passed  over  with  but  a  word  of  comment. 
The  pan  was  the  earliest  implement  used  in  separating  the  precious 
metal  from  the  accompanying  gravel  in  California  and  is  still 
necessary  to  the  prospector,  mill-man,  and  assayer.  It  is  made 
of  the  best  quality  of  Russia  iron,  generally  stamped  out  of  a 
single  sheet,  with  the  edge  turned  over  a  stout  wire.  The  usual 
dimensions  are:  Diam.  10  in.  at  the  bottom,  16  in.  at  top,  and 
2Y4  in.  deep.  The  angle  of  the  sides  is  37°.  The  method  of  use 
is  as  follows :  The  pan  is  filled  with  the  gravel  and  sand  and  then 
carefully  lowered  under  water;  the  fine  and  light  material  are 
gradually  washed  off,  care  being  taken  not  to  allow  any  gold  par- 
ticles to  escape ;  the  pebbles  and  coarser  material,  after  examination, 
are  removed  by  hand;  washing  continues  until  only  magnetic  sand 


INTRODUCTORY. 


17 


and  the  gold  remains.  The  pan  being  tilted  and  the  water  care- 
fully manipulated,  the  gold  forms  a  fringe  at  the  top  of  the  sand 
and  is  thus  collected. 


Fig.  4.     Bed  of  Gold-bearing  Gravel  in  the  Old  Workings 
9  at  Mississippi  Bar. 

The  'rocker'    is    a    box    about    4    ft.    long    and    2    ft.  wide, 
and  is  mounted  on  semicircular  pieces  of  wood  and  worked  by  a, 


18  DREDGING   FOR   GOLD   IN   CALIFORNIA. 

handle  to  give  it  a  side  motion ;  and  it  is  also  inclined  so  as  to  carry 
the  material  down  to  the  lower  end,  which  is  open.  At  the  upper 
end  is  a  small  hopper  that  may  be  removed  and  which  has  a 
sheet-iron  bottom  perforated  with  5^ -in.  holes.  Under  the  hopper 
is  a  canvas  apron  or  tray  inclined  toward  the  head  of  the  box 
but  touching  neither  end  of  the  hopper-box.  A  wooden  riffle  is 
placed  across  the  box  at  the  centre  and  another  at  the  end.  The 
material  is  fed  into  the  hopper  and  screened  through  by  water 
poured  on  top ;  the  lighter  material  is  carried  over  the  end,  while 
the  riffles  catch  the  gold  and  magnetic  sand.  This  residue  is 
panned  at  the  end  of  the  operation. 

The  'torn'  was  originally  a  rough  wooden  box,  14  ft.  long, 
and  2  ft.  wide  at  the  upper  end,  and  3  ft.  at  the  lower  end. 
The  sides  were  about  10  in.  high  and  the  bottom  had  six  or  more 
cleats  or  riffles.  The  water  was  fed  in  a  continual  stream  and 
the  material  treated  was  in  larger  quantities  than  the  rocker.  The 
next  step  was  the  'sluice-box' ,  which,  as  it  could  be  lengthened 
indefinitely,  had  a  much  larger  capacity.  It  is  generally  made 
in  sections  12.  ft.  long  and  from  1  to  2  ft.  wide.  Riffles  are 
placed  both  across  and  lengthwise  with  the  box ;  mercury  is  in- 
troduced and  the  gold  amalgamated. 

'Ground-sluicing'  came  next ;  it  consisted  in  bringing  water 
through  a  ditch  to  a  point  above  the  claim  high  enough  to  produce 
a  strong  current.  The  bottom,  if  possible,  is  on  bedrock  and 
large  stones  form  an  artificial  riffle.  Occasionally  a  wooden  sluice 
with  riffles  is  placed  at  the  end.  Large  quantities  of  material  are 
shoveled  from  the  sides  into  the  ditch.  The  stones  are  finally 
removed  and  the  concentrated  material  at  the  bottom  is  taken 
out  and  put  through  a  rocker  or  long  torn. 

'Booming'  or  'gouging'  is  somewhat  similar  to  ground- 
sluicing,  except  that  a  large  quantity  of  water  is  collected  in  a 
temporary  dam  above  the  workings  and  allowed  to  rush  down 
suddenly,  cutting  away  large  quantities  of  'pay  dirt'  which  is 
conducted  through  ground-sluices. 

The  gravels  were  first  tested  by  pan  and  rocker.  The  latter 
was  introduced  from  Georgia,  and  toward  the  end  of  1850  the 
long  torn  was  brought  into  use.  The  dry  bars  of  the  rivers  that 
were  easy  of  access  at  low  water,  were  first  worked  out;  then 
the  bottoms  were  worked,  by  using  wing-dams ;  and  finally  entire 


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be 


5 

P 


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20  DREDGING   FOR    GOLD   IN   CALIFORNIA. 

streams  were  deflected  from  their  course  by  flumes  and  ditches. 
The  lower  'bench  gravel'  was  then  worked  by  'torn'  and  other 
sluices,  booming,  and  gouging,  etc.  Gradually  these  benches  and 
low  alluvium  supplies  also  becoming  short,  attention  was  turned 
in  1852  to  the  high  hill  deposits — the  buried  rivers.  These  im- 
mense alluvial  banks,  often  capped  with  basalt,  sometimes  have 
a  depth^(or  'face')  of  over  600  ft.,  and  as  the  richest  stratum 
usually  lies  near  the  bottom,  the  grade  of  material  was  found  to 
be,  as  a  rule,  lower  in  gold  content  than  the  deposits  already  des- 
cribed. A  larger  scale  of  operations  and  more  economic  methods 
became  necessary.  This  was  done  by  hydraulicking,  the  directing 
of  jets  of  water  under  heavy  heads  against  the  bank,  which  is 
thus  disintegrated  and  washed  over  sluices ;  it  was  also  done  by 
drift  mining,  following  the  deposits  by  'tunnels'  under  the  hills 
or  reaching  them  by  shafts  on  the  flat  lands. 

Another  method  of  working  these  deeper  deposits,  particularly 
where  they  do  not  contain  water,  is  by  the  hydraulic  elevator,  an 
upright  pipe  into  the  bottom  of  which  the  gravel  is  drawn  by  a 
jet  of  water  under  head  that  also  raises  it  to  the  top  (sometimes 
40  ft.),  where  it  is  sluiced  in  the  usual  manner.  It  is  not,  however, 
proposed  in  this  article  to  enter  into  a  discussion  of  the  relative 
conditions  surrounding  the  most  advantageous  use  of  each  of  the 
methods  mentioned. 

In  the  later  'seventies  hydraulic  mining  had  become  one  of 
the  most  important  industries  of  California,  in  which  more  than 
$100,000,000  had  been  invested,  in  mines,  reservoirs,  canals,  and 
equipment,  but  owing  to  damage  done  to  farming  lands  in  the 
valleys  adjacent  to  the  Sacramento  river  and  its  tributaries,  this 
method  of  mining  was  inhibited  in  1880  by  Congressional  act,  and 
hydraulicking  was  almost  entirely  discontinued,  until  the  passage 
of  the  so-called  Caminetti  Act,  early  in  the  'eighties,  which  per- 
mitted the  resumption  of  hydraulic  mining  under  the  permit  and 
restrictions  of  a  corps  of  United  States  engineers,  known  as  the 
Debris  Commission. 

The   Debris    Commission's    work   is   directed   entirely   to   con- 
trolling the  natural  detrital  flow,  and  although  appointed  for  this 
work    about    1883    and    at    present     employing     conscientious    and 
efficient  engineers,  their  whole  work  to  date  has  been  confined  to , 
the  Yuba  river,  where  practical  results  were  only  accomplished  in 


INTRODUCTORY. 


21 


1904.  A  point  was  selected  a  few  miles  above  the  present  site 
of  Hammon  City,  where  it  was  proposed  to  place  a  dam,  the  duty 
of  which  was  to  arrest  the  burden  of  sediment  in  the  river  and 
collect  it  there.  The  height  of  the  dam  was  to  be  sufficient  for 
a  year's  accumulation  and  at  the  end  of  that  period  it  was  to  be 
added  to  year  by  year. 

It  is  commonly  supposed  that  the  efforts  of  the  Debris  Com- 
mission are  to  restore  the  practice  of  hydraulic  mining  throughout 
the  State,  but  such  is  unfortunately  not  the  case,  nor  does  there 


Fig.  6.     Spillway  of  the  Barrier  Dam  on  the  Upper  Yuba. 

appear  to  be  the  slightest  hope  for  a  largely  increased  output  from 
this  source  in  the  near  future.  It  is  true  that  under  certain  con- 
ditions— the  chief  of  which  is  that  the  miners  provide  impounding 
dams  or  settling  basins  for  the  tailing  they  produce — some  approved 
mines  may  continue  to  work,  but  the  formality  to  be  gone  through 
and  the  expense  of  this  work  as  a  rule  prohibit  large  workings 
and  the  output  from  such  mines  as  look  after  their  own  tailing  is 
inconsiderable  compared  with  the  product  of  former  hydraulic 
mining  or  what  might  be  produced  under  the  favorable  mining 
conditions  of  today. 


22  DREDGING   FOR    GOLD   IN   CALIFORNIA. 

After  several  abortive  attempts,  the  Yuba  dam  was  built  of 
piles  and  rubble,  and  capped  with  a  sheet  of  concrete  18  in.  thick. 
The  horizontal  distance  between  top  of  apron  to  end  of  toe  of  this 
first  portion  is  36  ft.  and  the  height  is  6  ft.  It  was  estimated 
that  the  annual  increase  necessary  would  be  about  8  ft. ;  but 
this  has  proved  to  be  an  over-estimate.  In  1906  eight  feet  were 
added  to  the  upper  side,  making  the  present  total  height  from 
original  base  14  ft.  and  the  width  from  top  of  present  apron  to 
toe  56  ft.  The  length  of  the  dam  is  1200  ft.  and  a  spill-way  is 
now  being  constructed  around  the  south  end.  Since  the  last 
addition  the  basin  has  filled  up  to  within  a  few  feet  of  the  top 
with  precipitated  material,  the  water  at  the  deepest  point  (near 
the  spill-way)  being  about  five  feet. 

Work  of  great  magnitude  too,  in  connection  with  this  im- 
pounding problem  is  being  carried  on  by  the  dredges  and  contract 
work  at  Hammon  City,  a  few  miles  below  the  barrier  dam.  These 
settling  basins,  especially  the  one  behind  the  barrier  dam,  should 
prove  a  valuable  experimental  ground  for  the  State  with  regard  to 
ascertaining  the  annual  accumulation  of  gold  brought  down 
by  the  river.  A  series  of  borings,  at  close  intervals  across  this  and 
the  other  basins,  through  the  material  deposited  there  since  their 
construction,  would  certainly  be  extremely  interesting;  at  any  rate 
it  would  give  some  data  of  the  amount  of  concentration  that  had 
taken  place  in  the  early  gravel  flows. 

An  ambitious,  though  seemingly  impracticable,  suggestion  has 
been  made  with  regard  to  assisting  the  resumption  of  work  by 
the  hydraulic  mines.  It  is  proposed  to  direct  the  tailing  toward 
the  worthless  tule  lands,  which  cover  a  vast  acreage  in  the  Sacra- 
mento valley,  and  it  has  been  contended  that  on  filling  these  swamps 
with  sand  and  gravel,  they  may  become  useful  for  agricultural 
purposes.  This  point  has  not  been  satisfactorily  settled  as  yet, 
'  though  at  the  present  time  it  is  understood  experiments  are  being 
made  with  that  end  in  view. 

As  stated  above,  the  districts  to  be  treated  in  this  article 
are  Oroville,  Folsom,  and  the  Yuba,  as  exemplifying  the  most 
modern  dredging  practice,  and,  as  few  mining  camps  are  surrounded 
by  such  pleasant  living  conditions,  a  descriptive  note  may  be 
appreciated  in  passing. 


24  DREDGING   FOR   GOLD   IN   CALIFORNIA. 

To  the  stranger  fresh  from  the  East,  the  first  view  of  the 
Sacramento  valley  is  a  new  sensation.  In  his  long  trip  across 
the  continent  he  has  no  doubt  seen  prairie,  desert,  and  magnificent 
mountain  peak,  but  looking  westward  from  the  vantage  point  of 
the  Sierras  is  a  scene  that  for  breadth  and  beauty  cannot  be  sur- 
passed. The  prairie  is  usually  rolling  and  its  horizon  is  but  a  few 
miles  away ;  the  desert  is  deadly  monotonous ;  here,  however,  is  a 
refreshing  change. 


Fig.  8.     Upper  Feather  River,  showing  the  Dam  Built  by  the  Golden 

Feather  Co.  at  an  Immense  Cost,  only  to  find  that  the  River 

Bottom  had  been  Worked  by  the  Miners  of  '49. 

From  the  lava-capped  heights  rising  abruptly  near  the  head- 
waters of  the  Feather  and  Yuba  rivers,  one  looks  over  a  broad 
expanse  of  valley  50  to  60  miles  wide.  In  the  near  foreground 
are  miles  of  orchard  land,  bearing  the  orange,  lemon,  pommelo, 
peach,  olive,  and  almond,  interspersed  with  far-stretching  vine- 
yards or  squares  of  wheat  and  grazing  land.  Silver  streaks  and 
patches  shimmering  in  the  bright  sunlight  denote  rivers  and  over- 
flowed levees.  Halfway  across  the  valley  the  jagged  peaks  of  the 
Marysville  buttes,  a  clear  blue  silhouette  20  miles  long,  thrust  them- 


INTRODUCTORY. 


25 


selves  abruptly  from  the  level  plain  to  a  height  of  1800  ft.  Further 
to  the  west,  the  Coast  Range,  a  long  low  band  of  still  fainter  blue, 
capped  occasionally  by  glint  of  sun  on  ice,  may  be  just  discerned, 
fading  from  sight  as  the  eye  traces  it  to  the  north.  Where  the 
Feather  river  escapes  from  the  mountains  and  immediately  below 


Fig.  9.     Marysville  Rapid  Transit. 

the  foothills,  nestling  among  its  orchards,  lies  Oroville.  The  name 
means  "city  of  gold,"  and  it  is  doubly  applicable  to  the  perennial 
color  of  its  fruit  and  the  precious  metal  contained  in  the  soil  on 
which  it  stands. 

Marysville  is  the  chief  town  and  distributing  point  for  the 
Feather  and  Yuba  river  dredging  districts.  It  is  one  of  the  oldest 
towns  in  the  valley  and  has  the  somnolent  atmosphere  of  one  of 
those  communities  in  the  Southern  States  not  yet  recovered  from 
the  effects  of  the  war.  Though  this  impression  -  may  belie  the 
real  commercial  activity  of  its  inhabitants,  it  is  strengthened  by 
the  sight  of  the  only  public  transportation  facility  afforded  by  the 
town — the  mule  cars — another  ante-bellum  reminder  from  the 
South.  On  the  Yuba,  28  miles  almost  due  south  from  Oroville, 
lies  Hammon  City,  also  situated  in  the  foothills,  and  named  from 
its  founder,  W.  P.  Hammon,  the  acknowledged  leader  of  the  dredg- 
ing industry.  The  site  of  this  settlement  was  only  established 
about  two  years  ago  and  though  comprising  but  a  handful  of 
buildings,  occupied  by  the  dredging  population,  and  temporary 


26  DREDGIN^.FOR    GO-ID.    IN   CALIFORNIA. 

shops  for  repair  work,  it  is  growing  fast  and  care  is  being  taken 
to  ensure  its  future  beauty  and  convenience.  The  main  street 
has  been  metalled  with  gravel  and  planted  on  either  side  with  rows 
of  black  walnut  and  palm  trees.  Such  older  trees  as  were  origin- 
ally on  the  ranch  have  been  left  standing  as  far  as  is  possible. 

The  town  of  Folsom,  best  known  as  the  site  of  a  State 
penitentiary  and  for  its  squalidness  amid  beautiful  surroundings, 
is  on  the  American  river  and  marks  the  northeastern  limit  of  the 
dredging  ground  on  that  stream. 


II.    PROSPECTING  DREDGING  GROUND. 

In  considering  the  prospective  value  of  dredging  ground  there 
are  many  conditions  to  be  taken  into  account  besides  its  actual  gold 
content;  it  is  like  all  other  classes  of  mines  in  this  respect.  As  a 
prominent  mining  engineer  recently  said:  "Each  mine  is  a  law 
unto  itself."  Likewise  each  dredging  scheme  must  be  considered 
strictly  on  its  own  merits  before  deciding  on  the  methods  and 
machinery  to  be  used.  Failure  to  recognize  the  specific  conditions 
affecting  a  property,  in  calculating  the  means  and  cost  of  working 
it,  has  entailed  the  loss  of  large  amounts  of  money.  Misrepresenta- 
tion and  'salting,'  too,  have  played  an  important  part  in  dredging 
as  in  other  kinds  of  mining.  Besides  the  amount  of  gold  and 
the  manner  of  its  distribution,  the  following  points  must  not  be 
overlooked : 

1.  Characteristics  of  the  gravel,  as  to  clay,  hardness,  cement- 
ing, size  of  boulders,  et  cetera. 

2.  Depth  to  bedrock ;  the  character  and  contour  of  the  rock. 

3.  Permanent    or    variable    water-level,    and    available    water 
supply  under  head  or  otherwise. 

4.  Costs  of  power,  labor,  transportation,  and  supplies. 

5.  Another  consideration;  not  seriously  affecting  dredging  in 
the  State  of  California,  but  to  be  taken  into  account  in  many  other 
localities,  is  the  climate. 

The  methods  of  determining  the  factors  mentioned  are  by 
sinking  shafts,  by  drilling,  and  by  actual  test  with  dredge.  Many 
diverse  opinions  have  been  expressed  as  to  the  relative  value  of 
each  method,  but  undoubtedly  the  most  practicable  is  the  shaft. 
Water,  however,  is  a  serious  drawback  to  prospecting  by  shaft 
and  therefore  drilling  is  more  common.  The  Keystone  drill  No.  3, 
boring  a  hole  of  6  in.  diam.,  is  generally  used  in  the  Sacra- 
mento valley  and  it  costs  about  $1700.  It  is  a  self-contained 
machine  and  consists  of  a  walking-beam  arrangement  and  an 
engine  of  8  or  10  h.  p.  In  drilling,  about  52  strokes  are  made, 
while  54  strokes  are  made  in  driving.  Casing  is,  of  course,  used  and 
a  shoe  with  steel  cutting  edge  and  weighing  800  Ib.  is  placed  on 
the  bottom  joint.  The  diameter  of  the  shoe  is  71/*  in.  outside  and 
this  diameter  was  used  affirst  in  calculating  the  area  excavated. 


28  DREDGING   FOR    GOLD   IN   CALIFORNIA- 

Exhaustive  tests  have  shown  that  the  actual  cubic  content  of 
the  core  brought  up  should  be  0.27  of  the  linear  depth  bored,  and 
though  this  is  greatly  modified  one  way  or  the  other — depending 
on  the  nature  of  the  ground — this  result  is  theoretically  true  for 
the  usual  standard  casing  (which  measures  S3A  in.  inside  diam.) 
and  it  has  been  arrived  at  by  measuring  the  content  removed  from 
the  sand  pump  after  drying.  Theoretically,  provided  that  all 
the  core  drilled  (and  no  more)  is  recovered,  16  in.'  should  be 
drilled  for  each  cubic  foot  of  core  produced.  It  will  be  found  that 
this  result  varies  from  that  obtained  on  the  assumption  that  the 
diameter  of  the  core  is  equal  to  the  diameter  of  the  outside  of 
the  shoe.  The  diameter  should  really  be  reckoned  about  midway 
between  the  outside  and  inside  diameter  of  the  drive  shoe,  thus 
allowing  for  the  wear  that  takes  place. 

The  practice  varies  as  to  keeping  the  casing  below  or  above 
the  bottom  of  the  drilling.  To  prevent  gold  from  a  rich  streak 
outside  the  area  of  casing  being  drawn  in  and  thus  making  the 
computation  valueless,  the  casing  is  kept  3  to  4  in.  below 
drilling.  On  the  other  hand,  if  the  casing  is  likely  to  strike  a 
large  boulder,  or  become  plugged  with  clay,  so  as  to  prevent,  for 
some  distance,  gold  being  extracted  that  really  belongs  to  the  core, 
then  the  drilling  is  kept  a  few  inches  below  the  casing.  Probably 
the  best  method  of  obviating  these  difficulties  is  by  drilling  below 
the  casing,  but  not  pumping  all  of  the  material  out  until  the  casing 
has  again  been  driven  and  drilling  resumed.  Conditions,  such 
as  hard  or  soft  ground,  old  workings,  etc.,  must  govern  this  part 
of  the  practice  so  that  sometimes  it  is  found  necessary  to  drive  the 
casing  much  below  the  drilling. 

The  sand-pump  is  a  hollow-steel  cylinder  8  ft.  long  and 
4  in.  diam.,  with  a  valve  at  the  bottom  and  a  closely  fitting 
plunger ;  on  each  side,  near  the  top,  it  has  an  oval  orifice  to  allow 
the  pulp  to  be  washed  out.  There  are  several  methods  of  treat- 
ment, and  the  general  practice  is  the  same  though  the  methods  of 
keeping  records  and  estimating  results  differ  slightly.  The 
apparatus  used  includes,  a  sluice-box  16  by  12  in.  and  10  ft.  long 
with  holes  at  the  lower  end  for  allowing  flow  into  a  four  compart- 
ment settling-tank,  another  settling-tank,  and  an  ordinary  rocker 
with  several  pans  and  tubs.  A  bucket  is  placed  in  the  sluice  and 
the  contents  of  the  pump  are  washed  into  this,  each  foot  being 


as 

be 
C 

'So 
.£ 


30  DREDGING   FOR   GOLD   IN   CALIFORNIA. 

treated  separately.  The  overflow  runs  off  into  the  settling-tank. 
The  content  of  the  bucket  is  panned  into  a  tub.  The  number  and 
size  of  the  'colors'  or  particles  of  gold  in  each  pan  are  estimated 
by  eye  and  the  result  of  each  foot  is  noted  in  the  log-book,  the 
colors  being  classed  in  three  sizes.  The  colors  and  black  sand 
from  each  pan  are  kept  separately;  the  former 'are  segregated  for 
each  foot  and  then  amalgamated.  The  gold  is  separated  by  nitric 
acid,  washed,  dried,  annealed,  and  weighed,  the  resulting  buttons 
from  each  hole  being  assayed  for  fineness.  The  surplus  contents. 
of  the  pannings  caught  in  the  tub  are  passed  through  the  rocker, 
the  concentrate  being  re-rocked.  The  overflow  runs  into  another 
settling-tank  and  the  contents  of  the  two  settling-tanks  are  roughly 
dried  and  measured,  the  computed  yardage  being  thus  checked. 

Another  method  is  as  follows :  The  material  from  the  hand- 
pump  is  received  in  a  pan  held  in  a  sluice-trough  similar  to  that 
mentioned  above.  The  slime  is  allowed  to  flow  away  and  the 
coarsest  material  is  panned  off  in  the  tank.  The  finer  portion 
of  the  material  in  the  pan  is  panned  over  a  large  metal  tub.  The 
estimation  of  'colors'  is  made  in  the  usual  manner,  and  everythin'g 
in  tub  and  trough  is  then  passed  over  a  rocker. 

Often  the  rich  material  in  the  interstices  of  the  bedrock  or 
a  rich  seam  will  continue  to  be  pumped  into  the  hole,  giving  higher 
pannings  than  are  warranted.  To  prevent  this,  when  within  a 
foot  or  so  of  the  bottom,  the  results  are  panned  as  usual  and  from 
the  foot  just  above  and  below  bedrock  the  concentrate  is  caught  in 
separate  pans  and  if  the  results  appear  unduly  high  they  are  dis- 
regarded. All  this  is  noted  in  the  log-book,  as  well  as  the  character 
and  amount  of  gold  content,  and  other  particulars  relating  to  the 
character  of  the  gravel. 

In  one  instance  I  observed  an  ingenious  method  of  preventing 
salting.  The  work  was  being  done  on  single  shift,  and  on  leaving 
for  the  night  two  panfuls  of  barren  tailing  were  dropped  down 
the  hole.  The  heavy  bit  with  rope  attached  was  then  lowered 
into  the  hole  and  the  iron  blocks  were  put  on.  To  move  these  it 
would  have  been  necessary  to  re-fire  the  boiler.  In  the  morning 
the  blocks  were  removed  and  the  rope  and  bit  washed  into  the 
hole  and  pounded  to  knock  off  any  'salt'  (gold  flakes)  that  might 
have  adhered  to  them  on  being  dropped  down.  The  pans  and 
sluice,  etc.,  were  thoroughly  washed  and  the  barren  tailing  at  the 


PROSPECTING    DREDGING    GROUND. 


31 


bottom  was  tested.      It  might  be  a  safer  plan  to  keep  a  watchman 
on  the  spot. 


Fig.    11.     Prospecting  Drill  and  Recovery  Process  on  the  Yuba. 

A  clever  case  of  salting  the  drillings  occurred  recently  at 
Oroville.  The  'salter'  mixed  some  finely  divided  gold  with  pipe- 
clay ;  he  became  so  adroit  that  he  could  mark  a  piece  of  casing  on 
the  inside  so  that  the  streak  would  contain  a  given  number  of 
cents  per  cubic  yard  to  be  drilled.  In  case  the  driller  noticed  the 


32 


DREDGING   FOR    GOLD   IN   CALIFORNIA. 


marks  at  all,  he  would  simply  think  that  they  were  initials  or  shop 
numbers,  and  during  the  process  of  drilling,  the  ^streak  with  its 
fine  gold  was  washed  into  the  pump  and  unwittingly  recovered  with 
the  gold  in  the  gravel. 

In  connection  with  salting,  several  cases  were  related  where 
the  drillers  wilfully  produced  (at  the  instance  of  their  employer, 
it  is  said)  misleading  records  by  the  following  method:  The 
bulk  of  the  gold  content  was  known  to  lie  in  a  stratum  3  ft. 
thick  and  between  17  and  21  ft.  from  surface;  each  hole  was 
drilled  to  about  30  ft.,  or  10  ft.  deeper  than  was* necessary.  To 
illustrate  the  result  we  will  assume  that  each  of  the  3  ft. 
between  17  and  21  ft.  contained  60c.  per  cu.  yd.  and  the  cost  of 
drilling  was  7c.  Thus  the  whole  ground  necessary  to  be  dredged 
(20  ft.  deep)  would  average  9c.  per  yd.,  leaving  a  profit  of  3c.  per  yd. 
worked.  The  crafty  party  who  attempted  to  wreck  the  negotiations 
for  a  fair  sale,  handed  in  his  report,  giving  the  depth  of  the  ground 
as  30  ft.,  and  the  average  yield  per  yard  as  6c.  Taking  the  vendor's 
admitted  cost  of  working  (7c.),  there  was  an  apparent  loss  of  Ic. 
per  yd. ;  and  so  the  sale  was  declared  off. 

The  following  examples  show  the  headings  used  in  the  log 
book  kept  by  drillers  of  the  Central  Gold  Dredging  Co.  and  from 
the  records  of  which  the  value  of  the  property  is  computed.  A 
summary  statement  is  attached  to  the  bottom  of  the  report  and  is 
made  up  of  details  under  the  headings  shown. 


.e 

Gold  Contents 

c 

en 

"cs 

Q 

"a 
Q 

Drilling  Data 

'ormai 

re 
§ 

1 

Estimated  Weight 

Number  of  Colors 

« 

gu« 

ssl 

O 

•s^« 

g 

S 

D 

I 

E 

3 



Q 

""S 

3*1 

PH 

5    Q 
o 



rt 
0 
CJ 

•o 

0) 

s 

£ 

S 
U 

TJ 
0> 

S 

E 





A  great  deal  has  been  said  about  the  extreme  care  necessary 
in  making  estimates  from  drill-records.  At  the  best,  the  method 
is  but  an  approximation  and  the  accuracy  with  which  it  is  done 


PROSPECTING    DREDGING    GROUND. 


33 


should  bear  an  exact  ratio  to  the  care  taken  in  measuring  the  bank 
and  calculating  the  cubic  content  dredged  each  month;  otherwise, 
the  results  are  not  only  misleading,  but  useless. 

Thus  the  value  per  cubic  yard  of  the  ground  at  each  particular 
hole  is  arrived  at ;  the  yardage  of  the  ground  necessary  to  be 
dredged  is  calculated  from  the  depths  to  which  the  'pay'  is  shown 
to  exist,  by  the  drill-records,  and  the  actual  average  value  per 
yard  is  determined  by  simply  multiplying  the  value  per  cubic  yard 
by  the  number  of  dredgeable  cubic  yards  in  the  property.  To 
estimate  the  purchasable  value  of  the  tract  the  first  cost,  depre- 
ciation, interest,  and  total  cost  per  yard  of  operation  must  be 
deducted  and,  -  of  course,  a  certain  percentage  allowed  for  the 
prospected  value  being  lower  than  the  recoverable  value.  One  of 
the  largest  operators  in  the  State  told  me  that  he  always  deducted 
at  least  40%  of  the  prospected  value  in  purchasing  dredging  tracts. 

As  to  the  number  of  holes  necessary  to  test  the  ground,  this 
also  is  arbitrary.  If  the  gold  is  known  to  be  evenly  distributed, 
the  tract  should  be  divided  into  five  to  ten  acre  squares.  A  flag 
at  the  centres  of  these  marks  the  site  of  the  hole.  If  the  gold  is  in 
narrowing  or  widening  channels,  the  ground  should  be  first  crossed 
by  series  of  holes  at  long  intervals  and  then  closer  together  if  favor- 
able results  are  indicated. 

The  cost  of  drilling  differs  with  the  conditions,  but  it  may  be 
said  that  the  price  per  foot  will  vary  between  $1  and  $3.75  per 
ft. — a  wide  range.  In  one  case  at  Oroville  13  holes  were  put 
down 'at  a  cost  of  $3.48  per  ft.,  and  in  the  same  district  at  another 
property  seven  holes  cost  $2.40  per  ft.  Some  contract  work  at 
Oroville  was  done  for  $2.50  per  ft.  The  following  recent  examples 
of  costs  and  speed  cover  a  large  area,  and  will  give  a  practical  idea 
of  the  variation:  On  the  Yuba,  five  holes  were  drilled  'to  an 
average  depth  of  93  ft.  at  an  average  cost  of  $3.85  per  ft.  The 
work  was  done  during  the  winter  rains  and  the  roads  were  ex- 
tremely heavy — freighting  was  difficult,  transportation  charges 
excessive,  and  there  was  great  delay  in  having  repairs  made  at 
Marysville  (the  nearest  point),  the  fixed  charges  having  to  be 
sustained  all  the  time.  Moreover  the  work  had  to  be  finished 
within  a  time  limit,  so  as  to  secure  results  before  an  option  on  the 
property  expired. 


34  DREDGING   FOR   GOLD   IN   CALIFORNIA. 

In  the  southern  part  of  the  Oroville  district  50  holes  were  put 
down  averaging  35  ft.  each  and  two  drills  were  employed  working 
simultaneously.  The  cost  in  this  case  averaged  the  extremely  low 
price  of  97c.  per  ft.  The  work  was  done  in  summer  and  all 
conditions,  including  soft  ground,  were  most  favorable.  Water 
was  close  at  hand  and  the  fact  that  both  drills  ran  under  the  same 
management  reduced  expenses.  The  labor  included  1  foreman,  2 
drillers,  2  helpers,  1  panner,  1  two-horse  team  and  1  teamster ;  the 
last  also  acted  as  water  carrier. 

At  Oroville  nine  holes  were  put  down  about  June,  1904,  and 
totaled  258  ft.  in  depth.  One  machine  was  used  on  single  shift 
and  33  days  were  employed  in  the  work  with  4  days  more  for 
moving. 

The  cost  was  divided  as  follows : 

Labor  Per  day.  Amount. 

Driller    at  $3.50  $129.50 

Pumpmen    "     2.50  92.50 

Firemen     "     2.50  92.50 

Water  Carrier  and  team "     4.00  148.00 

Panner     265.50 

Hire  of  drill..  .    133.33 


$861.33 

Fuel 70.00 

Supplies    68.60 


$999.93 

Average  number  of  feet  per  shift 7.8 

depth   of  holes 28.7  ft. 

Average  cost  per  foot  from  time  drill  was  hired 

to  return   (41  days) $3.88 

In  panning  and  for  the  boiler  800  gal.  were  used  per  shift. 
Cost  of  fuel  per  shift  $1.90  (using  coal). 

In  the  following  case  a  month's  work  is  selected  out  of  the 
seven  months  continuous  work  done  just  previous  to  June  1906 
and  in  which  15  holes  were  bored  to  an  average  depth  of  28  ft. 
During  the  month  selected  5  holes  aggregating  172  ft.  of  drilling 
were  put  down  and  cost  $514.86  or  an  average  of  $3  per  ft. 


<M 

bb 


36 


DREDGING   FOR   GOLD   IN  CALIFORNIA. 


Just  31  days  were  employed  in  the  work  and  Sl/2  ft.  were 
drilled  per  day.  The  above  work  was  done  in  extremely  wet 
weather  and  the  ground  was  very  tight.  At  some  drilling 
operations  in  the  Yuba  bottom  during  the  present  summer,  oil 
was  used  as  fuel  in  the  boiler  and  55  gal.  per  day  were  consumed 
at  a  cost  of  about  $1  per  gal.  The  cost  of  prospecting  a  tract  by 
drill-holes  varies  with  the  thoroughness  with  which  it  is  done  and 
for  practical  purposes  the  following  simple  calculation  prepared  in 
tabular  form  will  show  the  range : 

Cost  of  Drilling  100  Acres  for  Various  Depths 
Up  to  50  Feet. 


Amount  of  Drilling 

For 
Cost  per 

20  ft. 
foot  at 

For 
Cost  pe 

30  ft. 

r  foot  at 

1  Hole  per 

$1.50 

$2.00 

$2.50 

$3.00 

$1.50 

$2.00 

$2.50 

$3.00 

1  Acre  

$ 

•2  AAA 

$ 
A  AAA 

$ 
c  noo 

$ 

f.    AAA 

$ 

A    COO 

$ 

f\  OOO 

$ 

7  ^00 

$ 

o  ooo 

2     "     

1    ^OO 

7  AAA 

7  CAA 

9  noo 

7    7CTA 

?  noo 

-2  yen 

4  son 

3     "     

1   OOO 

1    3^ 

1   f\f^f\ 

o  OOO 

1    ^OO 

7    AAA 

?  ^00 

7  000 

4     "     

7CA 

1   000 

1    7^0 

1    ^OO 

i    i  7=: 

1    ^00 

1  R7^ 

7  7CA 

5     "     

600 

800 

1,000 

1,200 

900 

1,200 

1,500 

1,800 

Amount  of  Drilling 

c 

For  ' 
:ost  per 

to  ft. 

foot  at 

For  . 

"ost  per 

50  ft. 
foot  at 

1  Hole  per 

$1.50 

$2.00 

$2.50 

$3.00 

$1.50 

$2.00 

$2.50 

$3.00 

1   Acre  

$ 
6,000 

8,000 

$ 
10,000 

$ 
12,000 

$ 
7,500 

$ 

10,000 

$ 

12,500 

$   : 
15,000 

2     "     

3,000 

4,000 

5,000 

6,000 

3,750 

5  000 

6,250 

7,500 

3     "     

2,000 

2,666 

3,333 

4,000 

2,500 

3,333 

4,766 

5,000 

4     "     

1,500 

2,000 

2,500 

3,000 

1,875 

2,500 

3,125 

3,750 

5     "     

1,200 

1  600 

2,000 

2,400 

1,500 

2,000 

2,500 

3,000 

With  regard  to  the  ratio  of  recovery  between  dredging  and 
drilling  much,  of  course,  depends  on  the  method  and  care  employed, 
the  relative  efficiency  of  the  gold-saving  appliances  and  the  manner 
in  which  the  clean-up  is  accomplished.  Most  experienced  operators 
contend  that  however  carefully  the  operation  is  carried  out  (within 
the  practical  economic  limits)  and  using  the  best  of  gold-saving 
appliances  the  results  by  drilling  can  never  approximate  the  work 
of  sampling  and  estimating  an  orebody  underground.  It  might 
be  supposed  that  by  using  an  arbitrary  method  of  (over  or  under) 
estimating  the  drilling  results,  a  fair  idea  of  the  probable  recover- 
able value  might  be. arrived  at  and  if  the  results  bore  a  consistent 
relation  (greater  or  less)  to  the  recovery,  this  would  be  an  effective 
method,  but  such  is  unfortunately  not  the  case  in  practice.  The 


fO 

bi> 


38  DREDGING   FOR   GOLD   IN   CALIFORNIA. 

ratios  are  quite  irregular  and  results  vary  both  above  and  below 
the  returns  from  prospecting.  Only  one  general  rule  seems  to 
hold,  and  its  application  is  found  to  be  generally  true,  namely, 
that  when  very  high  results — 70c.  to  $3  say — are  got  by  drill,  the 
recovery  from  that  place  is  sure  to  be  lower.  Likewise  it  is  true 
in  practice,  that  ground  giving  very  low  results  from  the  drill, 
say  from  1  to  5  or  6c.,  generally  dredges  considerably  higher. 
Some  experienced  operators  go  so  far  as  to  say  that  drilling  is 
practically  useless  except  as  a  means  of  ascertaining  whether  gold 
is  actually  present  in  the  ground  or  not.  On  the  other  hand  at 
Folsom,  where  several  thousand  holes  have  been  put  down  and 
the  most  careful  records  kept,  it  is  asserted  positively  that  an 
average  approximating  about  90%  of  the  gold  shown  by  drilling 
has  consistently  been  obtained  in  dredging.  Be  that  as  it  may,  when 
it  is  explained  that  roughly  a  drill-sample  will  only  represent  some- 
thing like  -^ oWo  to  nnroTnnr  of  the  body  of  material  to  be  worked 
while  in  sampling  a  mine  probably  from  •&£$-$  to  !  olw  *s  taken  of 
the  orebody  (which  is  not,  as  a  rule,  less  homogeneous  than  the 
gravel  beds),  there  should  be  at  least  a  proportionate  difference  in 
the  working  results.  Moreover,  the  method  of  estimation  and 
selection  cannot  be  compared  for  accuracy.  The  following  authen- 
tic cases  are  extremely  interesting  in  this  connection :  In  front 
of  the  Boston  &  California  dredge  No.  I,  22  holes  were  put  down 
in  one  acre,  and  the  results  showed  that  the  ground  contained  60c. 
per  cu.  yd.  When  this  particular  acre  was  dredged,  just  30c.  per 
cu.  yd.  was  recovered.  In  another  instance,  25  holes  were  put 
down  on  one  acre  and  the  dredge  recovered  95%  of  the  estimated 
amount.  On  the  Delancy  tract,  the  results  of  dredging  recovery 
came  very  close  to  the  drill-estimate,  the  latter  being  very  carefully 
done. 

Several  holes  were  checked  by  dredge  at  Oroville  and  the 
report  illustrates  the  practical  application  of  the  rule  laid  down 
above,  as  follows: 

Estimated  value  Recovered 

Property.  from  drill-hole.  by  dredge. 

Gardella    tract    $0.50  $1.25 

3.00  0.75 

0.00  0.30 

Leggett  tract    3. 18           No  record 

Viloro    0.06  0.28 

1.44  0.30 

0.20  MO 

.  0.12  0.30 


PROSPECTING    DREDGING    GROUND. 


39 


Of  course,  the  closer  together  the  holes  are  put  down  and 
the  more  of  them  there  are  on  a  given  tract,  the  closer  the  general 
result  for  the  whole  tract  should  come  to  the  actual  recovery;  if 
the  work  is  properly  done,  a  fairly  accurate  idea  of  the  value  of 
the  property  may  be  obtained. 


Month 

Ground 
Dredged 

Prospect  Holes 
in  and  near 
acre  dredged 

Prospect 
Value 

Recovery 

Ratio  of  Pros- 
pect Value  to 
Recovery 

Cu.  Yd. 

Number 

Cents 

Cents 

Per  Cent 

January  .... 

20,340 

2 

15.35 

15.38 

100.20 

February    .  . 

32,000 

2 

15.35 

10.65 

69.57 

March   

41,160 

2 

37.70 

18.78 

50.00 

April    

50,760 

3 

37.70 

18.91 

50.00 

May  

47,700 

3 

16.25 

16.94 

104.24 

June  

40,750 

2 

10.35 

9.09 

87.% 

July    

44,380 

2 

11.45 

9.62 

84.02 

August  

39,300 

2 

11.45 

10.87 

94.93 

September  . 

41,600 

2 

4.40 

10.25 

230.00 

October  

48,460 

3 

5.25 

9.58 

182.43 

November.  . 

40,300 

3 

17.23 

8.37 

48.58 

December.  . 

46,400 

3 

17.23 

9.20 

53.40 

An  average  of  about  2|  holes  per  acre  were  drilled  on  the  area  dredged. 

For  the  12  months  ending  December,  1903,  the  Biggs  No.  1* 
dredge  of  the  Oroville  Gold  Dredging  &  Exploration  Co.,  Ltd., 
worked  474,610  cu.  yd.,  which,  according  to  the  estimate  from 
prospecting,  should  have  yielded  11.40c.,  the  total  recovery  averaged 
only  8.45c.,  or  76%  of  the  prospect  value.  The  same  dredge  for 
the  following  12  months  of  1904  dredged  493,150  cu.  yd.,  which 
yielded  12.32c.  per  cu.  yd.,  whereas  the  prospect  value  of  the  area 
worked  showed  from  the  drilling  tests  an  average  content  of 
16.64c.  per  cu.  yd.,  in  other  words,  a  recovery  was  obtained  of 
about  74%  of  the  estimated  value  by  drilling.  The  following 
details  of  the  above  cases  show  that  the  ratios  of  recovery  in 
cases  of  ground  dredged  after  one  or  two  drillings  vary  greatly, 
while  the  total  average  for  the  year  appears  to  maintain  a  fairly 
uniform  relation. 

In  another  district  in  the  Sacramento  valley  for  the  three 
months  of  March,  April,  and  May,  1906,  a  certain  dredge  recovered 
an  average  of  25c.  per  cu.  yd.,  where  prospecting  by  drill  had 
only  indicated  18c.  per  cubic  yard. 

Naturally,  careful  shaft-sinking  is  a  more  satisfactory  method 
of  testing;  it  ascertains  both  the  gold  contents  and  the  nature  of 


*  The  Biggs  No.  1  is  now  Exploration  No,  1, 


40  DREDGING   FOR   GOLD   IN   CALIFORNIA. 

the  ground  far  more  efficiently  and  thoroughly,  but  the  cost  is 
sometimes  prohibitive  in  wet  ground.  Otherwise  it  costs  less 
than  drilling.  The  so-called  China  shaft  is  the  method  usually 
employed  and  unless  one  has  seen  the  work,  one  wonders  how  it 
was  ever  accomplished  by  hand.  Probably  workmen  of  no  other 
nationality  would  do  the  work  or,  in  fact,  could  work  in  such  a 
narrow  compass. 

The  shafts  are  sunk,  circular  in  section,  3  ft.  in  diam., 
and  the  work  is  done  by  Chinese.  Two  men  will  do  from  5 
to  8  ft.  per  day ;  and  at  Oroville  the  contract  cost  is  $1  per  ft. 
Washing  and  estimating  content  will  cost  about  30c.  per  day  more. 
These  costs  are  for  all  work  above  water  level.  Below  that  level 
special  arrangements  have  to  be  made  and  it  is  often  altogether 
impracticable  because  'John'  is  decidedly  averse  to  working  while 
water  is  being  hoisted  over  his  head,  and  little  is  he  to  be  blamed 
for  his  objection.  In  more  than  one  case  he  has  sunk  such  shafts 
where  it  is  dry,  to  depths  of  40  ft.  and  over.  In  a  large  percentage 
of  cases  where  water  is  supposed  to  be  insurmountable,  a  centrifugal 
or  some  other  form  of  pump  could  be  installed  with  a  small  boiler 
and  the  work  accomplished.  A  shaft  5  ft.  square  was  sunk 
for  a  depth  of  40  ft.  within  a  few  feet  of  the  Feather  river  and 
on  a  level  that  at  times  was  covered  by  the  overflow.  In  this 
instance  of  successful  prospecting,  a  6  in.  centrifugal  pump 
(run  by  steam)  was  used.  The  cost  should  be  little  more  for 
such  work  as  electricity  can  now  be  successfully  and  economically 
used,  and  the  results  are  so  far  ahead  of  the  average  drill-hole — if 
only  for  the  purpose  of  positively  knowing  the  nature  of  the 
ground — that  were  cost  per  foot  several  times  more  than  drilling, 
it  would  still  be  advisable.  The  whole  area  of  a  certain  property 
at  Oroville  could  have  been  efficiently  and  cheaply  tested  in  this 
manner,  but  for  some  inscrutable  reason  drilling  was  resorted  to 
after  a  short  period.  Shaft-sinking  on  one  property  at  Folsom 
cost  $1  per  ft.  including  panning,  etc.,  and  an  average  of  9  ft.  per 
day  was  accomplished. 

The  only  instances  of  work  relating  to  the  so-called  paddock 
system  that  I  am  aware  of  in  the  Sacramento  valley  are  those 
cases  (cited  in  the  Bulletin  on  'Gold  Dredging'  published  by  the 
California  State  Mining  Bureau)  at  Oroville,  where  Messrs. 
Hammon  &  Treat  in  1895  sunk  a  pit  about  100  ft.  square  down  to 


PROSPECTING    DREDGING    GROUND.  41 

the  bedrock  and  used  a  centrifugal  pump  to  keep  the  water  out. 
The  gravel  was  hauled  in  wagons  to  small  sluice-boxes,  where  it 
was  washed.  In  the  other  case  the  water  was  found  to  be  too 
heavy  to  contend  with  on  approaching  bedrock.  This  work, 
however,  was  apparently  done  in  a  mining  way  and  not  as  a 
prospect  to  test  the  ground. 

Both  at  Oroville  and  Folsom  most  of  the  ground  now  being- 
worked  by  dredge  was  all  worked  over  years  ago  by  pan,  rocker, 
and  sluice  during  the  early  days.  As  the  grade  of  the  gravel  got 
lower,  the  white  men  left  and  Chinamen  took  their  places  and  the 
ground  was  re-worked.  In  the  dry  season  it  is  probable  that 
these  old  shafts  and  drifts  in  many  places  reached  the  present 
bottom  as  shown  by  the  timbers  and  portions  of  wing-dams 
that  are  encountered  by  the  dredges  and  drills  every  day — much 
to  the  operator's  disgust.  Even  in  wet  weather  some  of  the 
ground  was  probably  worked  to  the  bottom  with  the  assistance  of 
the  'China'  pump — a  contrivance  consisting  of  one  or  two  3  in. 
rubber  belts  with  wooden  blocks  attached  which  acted  as  elevators. 
This  was  either  driven  by  hand  or  by  an  overshot  wheel  of  native 
manufacture.  By  this  means  in  some  cases  the  water  was  pumped 
from  a  depth  of  40  feet. 

Although  not  thorough,  this  work  was  so  general  and  the 
district  was  so  carefully  exploited  that  today  it  is  said  that  ground 
where  old  workings  are  not  found  is  generally  poor,  and  actual 
values  of  15c.  per  pan  and  over  have  been  obtained  from  some  of 
the  old  tailing  beds.  These  abandoned  workings,  when  encoun- 
tered by  the  prospect  drill-holes,  however,  form  a  menace  which 
often  vitiates  entirely  the  result  of  the  hole,  as  it  is  impossible  to 
say  from  what  amount  of  gravel  the  results  are  produced.  The 
following  authentic  record  from  some  recent  prospect  holes  at 
Oroville  show  how  variable  is  the  distribution  of  the  gold.  In 
some  cases  it  seems  to  lie  in  well-defined  streaks  and  elsewhere  it 
is  disseminated  through  almost  every  foot  of  the  ground  to  be 
worked.  The  first  and  second  records  are  of  two  holes  on  the 
El  Oro  tract  at  Oroville  and  the  other  two  are  from  some  drilling 
near  the  centre  of  the  district,  both  on  the  same  property. 


42 


DREDGING   FOR   GOLD   IN   CALIFORNIA. 


On  El  Oro  Tract. 


Number  and 


coarseness 
of  colors. 

Depth 
in  feet 

1     "j 

.       2 

3 

4 

5 

6  . 

1  fine  

7 

8 
9 

10   j 

11    I 

1    

12    5 

3   
15   

13  I 
14 

2  

15 

1   

16 

1    

18    1 

19    1 

2  

20  J 

3  

21    ^ 

3     

22    } 
23    1 

..26 

27 

28 

29 

1   

30 

1   

31 

32    !> 

..34 

35 

36 

Trace    

37 

38 

39 

40   J 

Formation. 


Red  clay. 


Large  gravel  with 
little  red  clay. 

Loose  ground,  probably 
old  workings. 


}•  Large  wash. 


T 

Large  wash  but  very 


Solid  but  more  clay 
and  smaller  gravel. 


PROSPECTING    DREDGING    GROUND. 


43 


Record  of  a  Deep  Hole  on  El  Oro  Tract 


Depth  from 
Surface, 
Ft. 

Colors 

Remarks 

Formation 

9 

0 

Clay  and  soil. 

11 

11 

Fine 

Large  wash  and  clay. 

12 

1 

<  <         <  <         i  «       <  i 

15 

3 

"         "         "      "  and  some  sand. 

("2 

] 

?Q 

J3 

I 

Large    wash    and    clay    and    some 

£s 

|5 

r 

sand. 

17 

30 

11 

Large 

Same  as  above  but  softer. 

32 

17 

Medinm 

1  1      i  <       ii       ii           ii 

36 

*Extra  good 

•  <      i  <       i  <       i<           ii 

37 

i<         <  < 

Very  large  wash. 

44 

Good 

ii         ii         <i 

45 

0 

Changing. 

46 

ts 

Dead  looking  wash  . 

47 

0 

Sand  with  some  clay. 

66 

0 

"&  some  boulders. 

73 

0. 

Clay,  sand  and  mica. 

78 

0 

Sand. 

83 

10 

Very  fine 

Small  gravel. 

87 

2 

<i         ii 

Large       " 

91 

0 

Sand. 

99 

0 

Small  wash,  tough  clay. 

100 

0 

Large  wash. 

107 

0 

Country  rock. 

*In  this  and  the  next  two  records  below  the  number  of  colors  was  not  kept 
but  it  was  of  better  grade  than  the  upper  portion. 

fFormation  probably  volcanic;  colors  supposed  to  have  been  carried  down. 


44 


DREDGING   FOR   GOLD   IN   CALIFORNIA. 


Case   1. 


Depth 

Estimated   Weight 
in  Milligrams 

Number  of  Colors 

Formation 

Remarks 

Ft.    In. 

Coarse 

Medium 

<u 
c 

£ 

Coarse 

Medium 

V 

c 

£ 

Top-soil    stiff    and 

3 

1 

3 

t"        sticky. 

4 

1 

Very  stiff 

5 

6 

>   Hard  pan. 

1        casing 

7 

[ 

10 

drove 

12 

13 

Little    hard    pan    and 

hard. 

14 
15 

fine  gravel. 

J 

16 

1    Some  fine  and  medium 

1 

17    3 
18 
19 

0.1 

1 

[        gravel,   much  sticky 
clay  and  sand  . 

20    1 

O  1 

0.3 

2 

^    Much   medium    and 

Tight 

21 
22 
23    2 
24 

0.1 
0.1 
1.4 
5.5 

2 

5 
4 
12 

[_       coarse  gravel-. 
1    Little  sticky  clay  and 
J        some  sand. 

^        and 
heavy. 

26      $ 
26  111 
27  11| 
?Q    ? 

9 
0.4 
1 

15 
4 
3 

Y  Much   coarse  gravel 
and    sand.      Some 
1        clay  and  cement. 

£;/              Zr 

30 

1.5 

4 

f  Boulders. 
I 

-» 

31 

|    Very  coarse   gravel 

] 

32     1 
33     H 
33  11 
34    9 

much    sand    and    a 
!        little  sticky  clay. 
1    Coarse   gravel,    much 
sand    and    a      little 

1        Very, 
tight. 

J        sandy  clay. 

1 

PROSPECTING  DREDGING   GROUND. 


45 


Case  2. 


Depth 

Estimated  Weight 
in  Milligrams. 

Number  of 
Colors 

Formation 

Remarks 

Ft.    In. 

Coarse 

Medium 

0> 

c 

£ 

Coarse 

Medium 

• 

c 

£ 

2      1 

1 

5 

-  Topsoll  and  fine  gravel 

3 

1.3 

1 

2 

2 

1   Much    medium    and 

4 

2 

coarse   gravel    heavy. 

5 

.8 

Some  sand  and  clay. 

6 

1 

3 

7 

3 

7 

8 

.7 

5 

i    Soft 

9 

.2 

2 

1 

10 

.2 

1 

tight 

11      i 

8 

8.5 

4 

15 

12 

2 

3.5 

1 

7 

- 

and 

13 

2.3 

8 

14 

1.5 

4 

1 

6 

heavy. 

15 

.8 

4 

16 

.6 

4 

- 

17 

.3 

2 

18 

4.6 

8 

Extra  coarse  here. 

1 

19 

.3 

2 

1 

20 

1.3 

3 

21 

1 

2 

22 

2 

5 

23 

.5 

4 

, 

24 

.5 

2 

25 

1.5 

8 

Extra     coarse     c  e- 

26 

.6 

3 

mented  gravel. 

26    8 

.3 

2 

28 

1.7 

10 

» 

29 

.1 

1 

Much  sand 

30 

.6 

3 

and 

31 

32 

.2 
.2 

2 
3 

clay. 

j 

III.    DREDGING  MACHINES. 

Under  this  head  it  is  intended  to  describe  in  a  general  way 
the  construction  of  the  several  parts  of  a  dredge,  while  the  con- 
ditions under  w'hich  they  operate  and  the  relative  advantages  of 
each  are  gone  into  more  fully  in  the  following  chapters. 

There  is  practically  only  one  standard  type  of  economically 
successful  dredge  an  use  today  ih  the  Sacramento  valley  and  that 
is  the  endless  bucrcet  with  stacker.  Experiments  in  the  shape  of 
suction  dredges  (caissons  and  centrifugal  pump)  and  dipper  or 
steam-shovel  dredges  have  b.een  tried,  but  with  the  exception  of 
the  last  mentioned  (in  some  special  cases),  none  of  them  have  been 
successful.  There  are  only  two  dipper  dredges  now  working  at 
Oroville  and  these  will  be  described  in  detail. 

Fig.  14*/2  shows  the  development  of  the  California  dredge, 
through  the  single  and  double-lift  and  New  Zealand  types,  to  the 
present  machine. 

A  dredge  is  essentially  a  machine  to  excavate  and  recover 
the  precious  metal  from  gold-bearing  gravel  and  as  the  transporting 
medium  of  the  plant  is  water,  a  boat  or  scow  is  necessary  for  this 
purpose.  Thus,  a  dredge  consists  of  the  hull,  with  its  superstruc- 
ture and  housing ;  a  digging  ladder  and  chain  of  buckets ;  a  dis- 
integrating and  screening  apparatus ;  a  system  of  gold-saving 
devices;  pumps,  anchoring  arrangements,  and  a  stacker  for  the 
disposal  of  the  coarse  portion  of  the  material  excavated ;  and  the 
power-plant,  consisting  of  motors,  winches,  gearing,  etc. 

The  hull  is  built  in  scow  form,  the  forward  part  being  divided 
so  as  to  form  a  well,  in  which  the  ladder  and  bucket-chain  may  be 
raised  and  lowered.  As  the  main  wearing  parts — and,  in  fact,  the 
bulk  of  the  dredging  machinery — are  renewed  constantly  on 
account  of  wear  and  breakage,  the  hull  should  be  built  to  outlast 
the  original  plant,  and  indeed  to  outlast  the  area  which  it  is  intended 
to  work  over.  Great  care  should  be  exercised  in  the  design  to 
ensure  the  continued  strength  and  stiffness  so  essential  to  the  proper 
working  of  machinery.  Timbers  should  be  of  large  size  and  the 
main  truss  and  frame-timbers  should  be  full  length  without  splice. 
In  this  country,  wood  (Oregon  pine)  is  used  entirely  in  construct- 


a 

3 


A 


Fig.  14^2-     Diagram  Illustrating  the  Development  of 
the  California  Dredge. 


DREDGING    MACHINES. 


49 


ing  the   hulls,   and   steel   for  this   purpose   is   not  looked  on   with 
favor  by  dredging  men. 

As  an  example  of  the  method  and  material  of  construction, 
specifications  for  one  of  the  best  of  the  Oroville  boats  are  given 
as  follows :  The  deck  to  be  of  plank  4  in.  thick  and  6  in. 


Fig.  15.     Garden  Ranch  Dredge.     Dipper  in  Action. 

wide ;  on  the  sides  and  bottom  the  planking  to  be  4  in. 
thick  by  12  in.  wide;  the  sides  of  the  well  and  the  bulkheads  to  be 
of  plank  6  in.  thick  and  6  in.  wide.  The  sides  of  the  well 
are  extended  to  the  stern  of  the  boat  and  form  bulkheads  aft 
and,  in  addition,  there  are  two  other  bulkheads  running  the  full 
length  of  the  boat,  all  being  securely  fastened  to  the  framing 


50 


DREDGING   FOR    GOLD   IN   CALIFORNIA. 


timbers  of  the  hull,  and  firmly  tied  together  by  drift-bolts  driven 
through  the  edge  of  the  planking,  making  the  whole  bulkhead  a 
unit  in  much  the  same  manner  as  the  web-plate  of  a  girder.  Lateral 


Fig.  16.     Garden  Ranch  Dredge.     Crane,  showing 
Gearing  from  Rear. 

trusses  in  the  hull  and  superstructure  prevent  the  boat  from  sagging 
under  the  weight  of  the  machinery.  The  head-beam  is  steel,  built 
up  of  plates  and  angles,  and  the  back  guy  connections  are  so 


DREDGING    MACHINES. 


51 


arranged  that  torsion  is  practically  eliminated.  All  connections  are 
carefully  designed,  and  all  bolts  and  rods  are  as  large  as  experience 
has  shown  is  desirable,  and  the  washers  are  especially  designed  for 
this  work. 

Due   regard  must  be  given  to  the  fact  that  in  digging  hard 
ground  the  tendency  is  to  sink  the  stern  and  put  the  ends  of  sluices 


Fig.  17.     Exploration  No.  3  Dredge  being  Built  on  the  Bank. 

under  water,  and  the  centre  of  balance  is  also  changed  when  the 
ladder  is  raised  or  lowered.  The  hull  is  generally  built  on  stocks 
or  stilts  in  a  pit  previously  dug,  and  this  is  filled  with  water  after 
completion.  Often,  however,  it  is  built  alongside  the  pit  and 


52  DREDGING   FOR    GOLD   IN   CALIFORNIA. 

launched  into  it  later.  Each  joint  is  filled  with  white  lead,  caulked, 
and  the  whole  painted,  inside  and  out;  or  it  is  treated  inside  with 
crude  petroleum,  which  has  been  found  an  excellent  preservative 
against  water  and  dry  rot.  Hulls  are  always  provided  with  ventila- 
tors, to  prevent  dry  rot,  and  with  sea-cocks,  so  that  they  may  be 
sunk  in  case  of  fire. 

After  completing  the  hull  and  the  framing  of  the  gauntrees, 
etc.,  the  water  is  allowed  to  flow  into  the  pit  and  float  the  boat.  It 
is  then  launched  and  is  ready  to  receive  the  machinery,  after  the 
installation  of  which  it  is  housed  in.  In  floor-plan  the  design  is 
rectangular,  usually  slightly  rounded  toward  the  bow  and  divided 
by  the  well-hole  into  two  pontoons  forward.  The  dimensions  vary 
with  the  capacity  of  the  boat  and,  to  a  certain  extent,  at  the  will 
of  the  designer.  The  following  examples  of  large  and  small  boats 
in  the  three  districts  will  serve  to  give  an  idea  of  the  difference 
in  size. 

Capacity  of  Hull. 

bucket.  Length.  Width. 

District  Company.  cu.  ft.  ft.  ft. 

Oroville  Feather  River  Exploration  Co 3J4  80  30  - 

•"    5  80  32 

Lava  Beds  Dredging  Co 5  84  30 

Indiana  Gold  Dredging  Co 3  86  30 

Boston  &  Oroville  Mining  Co 4  88  30 

"    5  88  30 

Butte  Gold  Dredging  Co 3^  90  30 

Indiana  Gold   Dredging  Co 3  92  34 

Oroville    Dredging    Ltd 5  94  36 

Lava  Beds  Dredging  Co 5  96  36 

Yuba    Yuba  Consolidated  Gold  Fields 7]/2  115  40 

Oroville  Oroville  Dredging  Ltd 5  110  40 

Yuba    Yuba  Consolidated  Gold  Fields. . 7V2  115  40 

Folsom  El  Dorado   7  96  42 

Ashburton  Mining  Co 7l/2  110  50 

Folsom  Development  Co 8.9   •  120  49 

"     13  102  58 

The  depths  of  the  hulls  vary  between  6  and  7  ft.  and  the  draft 
from  3  to  Sy2  ft.  A  slight  camber  provides  drainage.  Most  hulls 
have  an  overhanging  deck  of  about  3  to  6  ft.,  which  allows  room  for 
blacksmith's  shop,  etc.  In  one  case  a  small  air-compressor  for  rivet- 
ing, etc.,  is  installed. 

Three  frames,  called  'gauntrees',  are  erected  on  the  hull  to 
support  different  parts  of  the  machinery.  The  middle  gauntree 


54  DREDGING   FOR    GOLD   IN   CALIFORNIA. 

supports  the  upper  tumbler  and  driving-gear  and  the  upper  end  of 
the  digging-ladder,  though  the  bearing  of  the  last  is  separate  from 
the  tumbler-bearing  except  in  some  of  the  later  boats.  The  chain 
of  digging-buckets  is  suspended  from  the  upper  tumbler  and  passes 
round  the  lower  tumbler  at  the  bottom  end  of  the  ladder. 

The  bow  or  forward  gauntree  is  used  for  hoisting  and  lower- 
ing the  digging-ladder  and,  incidentally,  the  landing-stage.  The 
stern  or  after  gauntree  supports  the  stacker  and  provides  guides 
for  the  spuds,  if  they  are  used.  The  gauntrees  are,  as  a  rule,  of 
wood,  though  the  Risdon  company  construct  their  middle  gauntree 
entirely  of  steel.  A  number  of  the  late  designs  of  bow  gauntrees 
have  steel  cap-pieces  and,  in  most  cases,  steel  guy-rods  are  used 
for  bracing  the  frames.  It  is  generally  recognized  that  the  type 
of  bow  gauntree  with  four  parallel  uprights  is  the  best,  as  in  those 
frames  designed  in  the  shape  of  the  letter  A  the  pontoons  spread 
and  tend  to  sink  on  the  inner  side.  Much,  too,  depends  on  a  proper 
form  of  bracing  between  the  bow  gauntree  and  the  superstructure 
behind.  This  and  the  general  methods  of  framing  will  be 
appreciated  on  consulting  the ' accompanying  photographs:  Fig.  19 
shows  the  A-shaped  gauntree.  Fig.  20  shows  the  typical  Risdon 
design  with  four  parallel  uprights.  Fig.  21  shows  a  steel-cap  frame 
and  a  method  of  solid  bracing  behind. 

The  digging  apparatus  includes  the  ladder,  the  bucket-line, 
with  the  buckets  and  their  parts,  that  is,  lips,  hoods,  bottoms,  pins, 
bushings  (and  links,  in  the  case  of  an  open-connected  line),  rollers, 
and  tumblers. 

The  ladders  and  bucket-lines  vary  in  length,  being  regulated 
by  the  depth  of  ground  in  which  they  are  working.  The  former 
is  built  of  steel,  though  in  one  of  the  original  boats  (now  defunct) 
the  ladders  were  of  wood.  At  Oroville,  where  the  average  depth 
of  gravel  is  about  30  ft.  below  water-line,  they  are  from  60  to  90 
ft.  in  length,  and  on  the  Yuba  the  longest  ladder  is  114  ft.  between 
centres  of  upper  and  lower  tumbler.  The  construction  also  varies 
according  to  the  fancy  of  the  designer;  and  they  are  generally 
formed  of  girder-sides  built  up  of  plates  and  angles,  and  braced 
across  the  top  and  bottom.  A  common  form  is  that  shown  in 
Fig.  15  where  the  sides  are  built  of  angle-irons  and  steel  plates 
with  alternate  plates  and  spaces  across  the  top  and  bottom ; 
the  top  and  bottom  plates  being  connected  by  another  plate  at 


DREDGING    MACHINES. 


55 


the  upper  end  to  form  bulkheads  to  prevent  accumulation  of 
dripping  mud  and  gravel.  Latticed  braces  of  angle-iron  are 
also  used.  Truss-rods  are  often  fastened  from  each  end  on 


Fig.  19.     A-Shaped  Forward  Gauntree  on  the  Ophir. 

the  bottom  to  give  extra  strength.  Another  form  of  ladder  (Fig. 
22)  is  braced  across  the  top  and  sides  with  lattice-work  of  angle- 
irons  instead  of  solid  plates,  and  still  another  form  built  of  angles 
with  plates  on  the  sides,  has  a  continuous  plate  from  top  to  bottom 


56 


DREDGING  FOR   GOLD  IN  CALIFORNIA. 


on  the  upper  side  (See  also  Fig.  23)  to  allow  the  surplus  dripping 
dirt  and  water  to  sluice  itself  to  the  lower  end,  where  it  may  be 


Fig.  20.     Risdon  Dredge  at  Fair  Oaks,  Bucket  7  Cubic  Feet, 
Electrically  Operated. 

again  picked  up  by  the  buckets.  It  is  doubtful  whether  this 
arrangement  proves  practical,  particularly  when  digging  deeply, 
as  once  the  dirt  strikes  the  water,  the  flow — particularly  of  the 


DREDGING    MACHINES. 


57 


fine  material — is  impeded.  At  the  top  and  bottom  ends  of  the 
ladder  steel  castings  are  built  in,  to  support  the  frame  and  carry 
the  lower  tumbler. 

Rollers  are  provided  on  the  upper  side  at  intervals  of  from 
5  to  7  ft.  to  reduce  the  friction  of  the  bucket-line  and  prevent 
excessive  wear  on  the  ladder.  Fig.  24  shows  a  digging  ladder 
fitted  with  rollers  and  ready  for  erection.  These  are  generally  of 
cast  iron,  sometimes  hollow  and  sometimes  solid.  In  a  few  cases 
manganese  steel  has  been  used. 


Fig.  21.     Forward  Gauntree  on  Boston  No.  4  showing  Steel  Cap  and 
Method  of  Bracing  in  Rea,r. 

The  tumblers  are  the  heavy  revolving  castings  at  the  top  and 
bottom  ends  of  the  bucket-line  round  which  the  chain  of  buckets 
revolves.  In  section  they  are  either  square,  pentagonal,  or 
hexagonal,  and  the  shape  is  governed  largely  by  the  theory  of  the 
designer.  In  Risdon  dredges  the  upper  tumbler  is  always  square 
and  the  lower  tumbler  is  generally  pentagonal,  the  idea  in  having 
them  different  being  to  avoid  the  resultant  jerk  caused  by  the 
buckets  leaving  the  peaks  of  upper  and  lower  tumbler  simul- 


,40 


60 


DREDGING  FOR   GOLD  IN  CALIFORNIA. 


taneously;  as  a  matter  of  fact,  the  jerk  is  largely  caused  by  the 
fact  of  having  a  square  upper  tumbler  instead  of  one  of  five  or 
six  sides.  With  the  deep  and  narrow  Risdon  bucket,  however, 
it  is  more  or  less  necessary  to  use  an  upper  tumbler  of  square 
section  to  insure  complete  dumping  of  the  contents  into  the  hop- 
per. The  irregular  wear  on  pins  and  bushings  soon  obviates  the 
jerk  caused  by  tumblers  of  the  same  section  by  elongating  the 


Fig.  24.     Rollers  on  Digging-Ladder,  No.  3  Folsom. 

bucket-chain;  this  wear  affects  the  length  of  chain  to  such  an 
extent,  that  usually  from  one  to  three  buckets  have  to  be  removed 
after  a  short  time  to  take  up  the  slack. 

The  question  of  increasing  the  number  of  sides  in  tumblers 
so  that  they  more  nearly  approach  a  circle  in  section  has  been 
discussed  many  times,  and  the  question  has  now  been  pretty 
well  settled  by  practical  experiment.  The  number  of  sides  must 


DREDGING    MACHINES. 


61 


remain  limited  for  two  reasons :  1 .  In  the  case  of  the  upper 
tumbler,  after  increasing  the  number  of  sides  to  six,  its  essential 
duty  of  holding,  pulling  round,  and  dumping  the  bucket-line  is 
impaired  and  no  practical  solution  in  the  shape  of  a  sprocket 


Fig.  25.     Lower  Tumbler  of  Folsom  No.  4,  showing  Wearing  Plate. 

arrangement,  any  more  than  is  now  formed  by  the  lugs  and  bot- 
toms, as  has  been  suggested,  has  been  evolved;  nor  is  it  likely 
to  be,  on  account  of  the  immensely  increasing  weights  and  con- 
sequent strains  set  up.  2.  The  objection  to  the  lower  tumbler-section 


62 


DREDGING   FOR   GOLD   IN   CALIFORNIA. 


being   increased   to   more   than   six   sides   or   seven   as   a   limit,    is 
chiefly  on  account  of  the  slippage  and  consequent  wear. 

The  chief  considerations  that  control  the  shape  of  the  upper 
tumbler,  however,  are  those  which  make  for  the  most  efficient 
and  thorough  emptying  of  buckets  when  dumping  into  the  screen- 
hopper,  and  the  least  wear  on  pins  and  bushings.  To  aid  this, 
jets  of  water  are  often  used,  playing  into  the  full  bucket  as  it 
rotates  over  the  upper  tumbler. 


Fig.  26.     Lower  Tumbler  Casting  of  Digging-Ladder. 

The  tumbler  is  not  only  constructed  of  different  sectional 
shape  but  of  different  design.  Some  of  the  old  patterns  were 
of  one  solid  casting,  necessitating  the  rejection  of  the  whole 
apparatus  after  a  comparatively  little  wear.  Nowadays,  however, 
tumblers  are  almost  universally  made  with  wearing  plates  or 
shoes  and  riveted  onto  the  castings,  so  that  they  can  be  removed 
at  intervals  and  thus  the  life  of  the  tumbler  is  much  increased. 
The  metal  used  in  these  wearing  parts  is  usually  nickel  steel  or 
manganese  steel. 


DREDGING    MACHINES. 


63 


As  has  been  mentioned,  the  lower  tumbler  is  supported  on 
bearings  in  the  casting  forming  the  lower  end  of  the  ladder, 
while  the  upper  tumbler  is  supported  by  bearings  in  a  steel  bed 
incorporated  into  the  middle  gauntree.  An  improvement  in  the 
lower  tumbler  is  the  addition  of  solid  cap-pieces  around  the  ends 


Fig.  27.     Lower  Tumbler  on  the  Ophir. 


of  the  shaft  outside  the  hub.  These  form  grease-cups  and  pre- 
vent the  ingress  of  grit  and  dirt.  Compression  grease-cups  are 
used  throughout  the  ladder  and  bucket-line. 

The  size  of  shafting  has  been  necessarily  increased  with  the 
greater  size,  capacity,  and  strength  of  the  modern  boats,  and 
upper  tumbler-shafts  may  now  be  seen  of  18  in.  diameter. 

The  bucket-line  is  undoubtedly  the  most  important,  as  well  as 


64 


DREDGING   FOR    GOLD   IN   CALIFORNIA. 


the  most  expensive,  part  of  a  dredge,  both  in  first  cost  and  main- 
tenance.      The    buckets    with   their    pins    and    bushings    constitute 


Fig.  28.     Close-Connected  Bucket  Line  on  the  Butte. 

the  most  vulnerable  part  of  the  machine  and  consequently 
necessitate  more  constant  repair  than  any  other  part.  The  line 
may  either  be  open-connected,  as  in  the  Risdon  type,  or  close- 


DREDGING    MACHINES. 


65 


connected,   as   in   all   other   designs.       In   the   first   case   a   link   is 
interposed   between   each   bucket    and   in   the    second   the   bucket- 


Fig.  29.     Open-Connected  Bucket  Line  on  the  Baggette, 
showing  the  New  Solid-Forged  Links. 

bottoms  form  the  links,  the  rear  eye  of  one  being  connected  to 
the  front  eye  of  the  one  behind  by  the  pin.  The  bucket  includes 
a  'bottom'  or  'back' ,  a  'hood'  and  a  'lip' ,  and  these  are 


66  DREDGING   FOR   GOLD   IN   CALIFORNIA. 

fastened  together  with  a  pin  and  bushings.  The  bottom  is  a 
solid  casting  of  high  carbon  or  nickel  steel  and  very  heavy.  It 
takes  the  wear  on  the  tumblers  and  when  the  metal  at  the  eye 
wears  down  to  breaking  thinness  it  has  to  be  discarded.  It 
weighs  from  about  500  Ib.  in  the  case  of  a  3  cu.  ft.  bucket  up  to 
2150  Ib.  for  a  13  cu.  ft.  bucket.* 

The  pins  are  made  from  a  variety  of  iron  and  steel,  as  will 
be  shown  later  on,  and  they  also  vary  in  diameter;  the  half- 
bushings  are  made  almost  exclusively  of  manganese  steel.  The 
hoods  vary  in  pattern  and  are  made  in  several  sections  riveted 
together,  or  in  one  solid  casting  or  forged  piece.  The  solid  cast- 
steel  hood  is  coming  into  general  use  now  and  will,  it  is  thought, 
supplant  the  other  sectional  rolled  types.  The  lips  are  an  import- 
ant part  of  the  bucket  and  as  they  take  the  greatest  wear  they  are 
most  often  renewed.  The  parts  of  modern  buckets  are  designed, 
however,  to  out-last  each  other.  The  lips  are  of  nickel  or  man- 
ganese steel  and  in  buckets  of  different  capacity  they  are  from 
1  to  2l/2  in.  thick,  and  8  to  14  in.  deep. 

Hoods,  lips,  and  bottoms  are  all  riveted  together  and  the 
capacity  of  the  complete  bucket  varies  from  3  cu.  ft.  to  13  cu.  ft. 
These  are  the  largest  and  smallest  in  use  in  the  Sacramento 
valley,  but  the  rating  is  arbitrary  and  usually  refers  to  the  theoret- 
ical capacity  in  wet  sand  and  not  to  bank  measurement,  which 
would  be  considerably  more. 

The  original  idea  of  an  open-connected  bucket-line  was  that 
it  would  dig  better  in  hard  ground  and  in  large  boulders,  but  the 
majority  of  boats,  in  fact,  all  modern  boats  except  those  of  the 
Risdon  type,  use  the  close-connected  line  in  preference ;  with  the 
latter,  more  ground  can  be  dug  in  the  same  time  under  the  con- 
ditions that  exist  in  the  districts  referred  to. 

Buckets  differ  greatly  in  shape,  the  chief  differences  being  in 
length  of  'pitch',!  angle  of  lips,$  comparative  depth  and  width. 

The  tendency  has  been  to  increase  the  diameter  of  the  pins 
on  the  larger  boats  and  they  are  now  made  as  thick  as  4l/2  in.  Some 
of  the  pins  in  the  earlier  Risdon  type  boats  (still  working)  are  less 
than  2l/2  in.  diam. ;  indeed,  it  is  related  that  the  pins  used  in  a 


*   The  bucket  of  this  capacity  weighs  3200  Ib.   complete. 

t  The  'pitch'  of  a  bucket-line  is  the  distance  between  the  centre  of  any  pin  and 
that  of  the  pin  in  the  next  adjacent  bucket. 

J  This  varies  with  the  angle  at  which  the  digging  ladder  is  operating  and  on  the 
amount  of  wear  that  has  taken  place. 


55 

c 
.2 

I 

"a 
x 
W 


be 


68  DREDGING   FOR    GOLD   IN   CALIFORNIA. 

bucket-line  of  one  of  the  first  boats  built  in  the  State  were  common 
l/2-in.  carriage  bolts  and  the  links  were  of  tire  iron  y%  by  2-in.  sec- 
tion. The  increase  in  size,  weight,  and  strength  has  been  extremely 
rapid  and  applies  to  nearly  every  part  of  the  dredge  subjected  to 
wear  or  strain. 


Fig.  31.     Bucket  of  13  Cubic  Feet  Capacity,  on  Folsom  No.  4. 

The  buckets  dump  over  the  upper  tumbler  into  a  hopper,  the 
steel  bottom  of  which  is  soon  covered  with  a  layer  of  boulders, 
preventing  the  damage  that  would  otherwise  result  from  the  con- 
tinual hammering.  On  the  Yuba  boats  an  idler-wheel  is  used,  as 
the  bucket-line  is  so  long  that  otherwise  it  would  scrape  on  the 


DREDGING    MACHINES. 


69 


grizzly  edge  of  the  well.      This  arrangement  is  described  in  Chap- 
ter VI. 

Jets  of  water  under  head  are  used  to  assist  the  automatic  empty- 
ing of  the  buckets  as  they  turn  over  the  upper  tumbler  and  are 
particularly  useful  when  clay  is  encountered  or  in  the  case  of  deep 
narrow  buckets,  such  as  the  Risdon  type.  They  are  arranged  in 


Fig.  32.     Bucket-Emptying  Jets  on  the  Butte. 

several  ways;  one,  two,  or  three  jets  (composed  of  pipe  from  3 
to  4  in.  diam.)  may  be  placed  vertically  over  one  another 
and  be  directed  at  different  angles  into  the  bucket  or  one  may  be 
placed  at  each  side,  or  again,  one  may  be  placed  at  each  side  and  one 
at  the  centre;  several  variations  in  arrangement  may  be  given  by 


70 


DREDGING   FOR    GOLD   IN   CALIFORNIA. 


changing  the  elevations  and  direction  at  which  the  jets  are  dis- 
charged. 

The  material  is  delivered  from  the  hopper  to  the  screen,  whose 
duty  it  is  to  disintegrate  and  classify  the  material  passed  through 
or  over  it.  The  two  types  of  screen  in  use  are  the  flat  shaking  screen 
of  which,  in  most  boats,  two  are  used  (one  beyond  the  other,  or 
one  above  the  other),  and  the  cylindrical  revolving  trommel,  varying 
in  diameter  from  3  ft.  6  in.  to  6  ft.,  and  in  length  of 
actual  screening  surface  from  14  to  21  ft.  The  largest  trommel 


Fig.  33.     Stacker  Discharge  on  Folsom  No.  4. 


in  use  is  on  the  Yuba  and  is  30  ft.  long  over  all.  The  dimensions 
of  the  shaking  screens  in  use  are  approximately  as  follows :  Upper 
screen,  from  12  by  4  ft.  6  in.  to  16  by  9  ft.,  and  lower  screen,  from 
12  by  5  ft.  to  16  ft.  by  9  ft.  9  inches. 

Probably  the  largest  combined  superficial  area  contained  in 
any  shaking  screen  is  afforded  by  those  on  the  Folsom  Development 
Go's  No.  4  boat,  which  give  300  sq.  ft.  The  question  of  the  relative 
advantages  of  trommel  and  shaking  screen  is  discussed  in  Chap- 
ter VI. 


DREDGING    MACHINES. 


71 


The  duty  of  the  stacker  is  to  take  care  of  the  over-size  from 
the  screens  and  to  deliver  it  at  such  a  point  behind  the  boat  that 
it  will  not  interfere  with  its  navigation. 


Fig.  34.     Belt-Conveyor  on  Exploration  No.  2. 

The  stacker  is  either  a  belt-conveyor  or  is  of  the  pan  form. 
The  former  requires  less  repair  and  consequently  entails  less  loss 


72 


DREDGING   FOR    GOLD   IN   CALIFORNIA. 


of  time — one  of  the  most  important  items  in  reducing  the  cost  of 
dredging;  but  it  usually  needs  to  be  replaced  oftener  and  at  a 
large  expense.  The  concensus  of  opinion  among  dredge-men  con- 
nected with  the  operation  of  the  larger  boats  favors  the  belt  as  a 


Fig.  35.     Belt-Conveyor  Stacker  on  Folsom  No.  4. 


DREDGING    MACHINES.  73 

method  of  conveying  the  gravel  from  the  screens,  at  least  in  boats 
using  buckets  of  5  cu.  ft.  capacity  and  over.  The  photographs  show 
the  two  forms  of  stacker.  A  pad  belt  is  often  used  to  reduce  the 
wear  on  the  main  belt.  Motive  power  for  the  pans  or  belt  was  for- 
merly supplied  from  the  boat,  but  now  in  almost  every  case  the 
motor  is  placed  on  the  outboard  end  of  the  stacker-ladder. 

A  belt-conveyor  may  not  advantageously  be  placed  at  a  greater 
angle  than  about  19°,  while  a  pan-stacker  will  carry  material  at  35°. 
The  length  of  the  stacker-ladder  changes  with  the  depth  of  ground 
to  be  dug,  as  does  the  digging-ladder,  for  in  deep  ground  the  boat 
does  not  move  ahead  so  quickly  and  a  larger  amount  of  material 
has  to  be  discharged  at  the  stern ;  therefore  to  prevent  grounding,  it 
must  be  deposited  at  a  greater  distance.  To  carry  the  belt  over 
the  ladder,  'idlers'  are  placed  at  every  few  feet  in  sets  of  three, 
four,  or  five,  arranged  in  convex  form.  The  latter  is  probably  the 
best  arrangement  as  the  curve  is  more  even  than  in  the  other  cases. 
With  three  idlers  there  are  two  points  of  more  or  less  abrupt  bend- 
ing, but  with  four,  a  V-shape  is  given  to  the  belt,  tending  to  crack 
it  at  the  centre.  This  is  more  particularly  the  case  in  broad  and 
heavy  belts  and  has  been  found  to  be  the  case  on  the  44-in.  belt 
used  on  the  No.  4  Folsom  Development  Go's  boat.  In  one  or  two 
cases  a  practically  flat  belt  with  one  cylindrical  roller,  slightly  con- 
cave at  the  Centre,  is  used  and  it  is  difficult  to  see  why  this  or,  in 
some  cases,  a  perfectly  flat  belt  is  not  the  best  that  can  be  used.* 
Side  boards  with  canvas  attached  to  them  are  used  and  the  continual 
curving  and  flattening  of  the  belt  that  takes  place  at  the  point  of 
discharge  is  obviated  and  the  wear  is  considerably  reduced.  Besides, 
the  whole  width  of  the  belt  is  utilized  as  a  carrier  and  the  injurious 
sluicing  effect  of  the  water  is  not  so  pronounced.  In  a  climate 
where  frost  is  prevalent,  belt-conveyors  are  not  advisable. 

The  following  excellent  notes  on  the  electric  equipment  and 
transmission  are  supplied  to  me  by  Mr.  George  L.  Holmes. 

"The  fact  that  most  of  the  dredges  in  California  and  in  fact 
all  of  the  dredges  in  the  Oroville,  Yuba,  and  Folsom  districts  are 
driven  by  electricity  has  caused  their  development  along  different 


*In  this  connection  Mr.  W.  P.  Hammon  says  however :  "We  have  just  discarded 
a  flat  belt-conveyor,  because  the  material  spreads  to  the  side  board  and  is  retarded  by 
friction,  creating  an  extra  load,  and  further  the  canvas  on  the  side  boards  is  a  con- 
tinuous source  of  trouble  when  digging  formation  containing  clay  or  mud.  Our  expe- 
rience is  that  the  power  consumption  is  increased  nearly  50  per  cent  with  this  form 
of  belt." 


74  DREDGING   FOR   GOLD   IN   CALIFORNIA. 

lines  than  in  districts  which  are  not  so  favored.  As  a  power  for 
dredging  purposes,  electricity  cannot  be  excelled  if  proper  precau- 
tions are  taken  and  the  installation  is  correctly  designed.  Those, 
however,  who  have  been  using  steam-dredges  and  have  remodeled 
their  equipment,  installing  motors  in  place  of  their  engines,  have 
come  to  grief.  The  reason  is  plain;  when  running  by  steam  the 
boilers,  engines,  etc.,  are  usually  designed  so  that  the  engines  will 
stall  before  the  driven  parts  are  strained  to  a  point  of  rupture.  If 
the  dredge-master  hangs  a  monkey-wrench  or  an  old  boot  filled  with 
gravel  on  the  safety-valve  lever  and  carries  a  higher  pressure  than 
\vas  intended,  for  a  short  time,  to  carry  him  through  a  tough  piece 
of  digging,  he  is  correspondingly  careful  while  the  increased  steam- 
pressure  is  being  carried.  Electricity,  on  the  other  hand,  is  brought 
to  the  dredge  from  a  power  plant  generating  perhaps  thousands  of 
horse-power,  over  wires  of  a  size  sufficient  to  prevent  an  excessive 
'line  loss'  and  the  main  motors  are,  in  the  latest  practice,  usually 
operating  under  the  full  voltage  of  the  line.  The  induction  motors  in 
most  cases  will,  before  stalling,  deliver  for  a  short  interval  from  one 
and  one-half  times  their  rated  capacity  to  twice  or  three  times.  Of 
course  precautions  are  taken,  the  motors  are  fused  to  cut  out  at  25% 
over-load  over-load  circuit-breakers,  etc.  are  installed ;  in  fact,  every- 
thing is  done  to  prevent  an  excessive  load  being  transmitted  to  the 
dredging  machinery.  These  precautions  however  really  do  not  pre- 
vent entirely  the  transmission  of  severe  shocks  and  strains  to  the 
machinery,  as,  for  instance,  when  the  buckets  strike  a  large  boulder 
or  other  comparatively  immovable  obstacle  and  are  practically 
stopped  instantly  thereby,  while  the  motor  jumps  from  its  normal 
power-delivery  to  two  or  three  times  the  normal  before  the  fuses  or 
circuit-breakers  act.  Of  course  the  cut-outs  act  with  'electrical 
speed'  but  even  so,  there  is  an  interval  between  the  stopping  of  the 
bucket  and  the  blowing  of  the  fuse  in  which  mischief  may  be  done. 
In  modern  practice,  the  designer  selects  the  motor  which,  with  his 
previous  knowledge  of  the  art,  he  believes  will  be  sufficiently  power- 
ful to  drive  the  buckets,  in  the  average  digging  to  be  encountered 
in  the  tract  to  be  worked,  at  the  maxium  efficiency  of  the  motor. 
In  heavy  ground  this  motor  will,  of  course,  be  overloaded  and  vice 
versa.  The  digging  apparatus  then  will  be  designed  to  withstand 
the  pull  caused  by  this  motor  when  running  at  50%  overload  and 
with  an  ample  factor  of  safety  beyond  this. 


76  DREDGING   FOR   GOLD   IN   CALIFORNIA. 

"In  the  Oroville  district  we  find  that  the  electric  power  is  man- 
ipulated in  various  ways,  to  serve  the  required  purpose.  Some,  with 
a  sort  of  insensate  fear  of  the  higher  voltages,  transform  the  current 
on  shore  to  440  volts,  use  a  ponderous  cable  for  conducting  the 
current  on  board,  and  have  a  comparatively  heavy  line-loss  on 
account  of  the  low  voltage.  Others  carry  the  current  on  board  at 
4000  volts  and  transform  to  440  for  all  the  motors,  while  some  use 
the  current  at  2000  to  2200  volts  for  the  larger  motors  and  transform 
only  for  motors  under  50  h.  p.  Each  practice  has  its  adherents  and 
its  wordy  arguments.  The  best  plan,  all  things  considered,  is  un- 
doubtedly the  last  mentioned,  inasmuch  as  the  losses  from  line, 
transformers,  etc.,  are  minimized.  This  plan  has  been  adopted  as 
best  by  the  Yuba  and  Folsom  companies.  The  usual  equipment  for 
a  5  cu.  ft.  continuous  bucket  dredge  of  the  type  commonly  in  use  at 
Oroville  consists  of  the  following: 

75  or  100  h.  p.  variable  speed  motor  for  driving  the  buckets. 

50  h.  p.  constant  speed  motor  for  main  pump. 

20  h.  p.  constant  speed  motor  for  screens. 

20  h.  p.  constant  speed  motor  for  stacker. 
5  h.  p.  constant  speed  motor  for  priming  pump. 

40  h.  p.  constant  speed  motor  for  sand  pump. 

20  to -25  h.  p.  variable  speed  motor  for  mooring  winch. 

3  to  30  k.  w.  O.  D.  type  transformers  for  the  motors  under 
50  h.  p. 

1  to  10  k.  w.  O.  D.  type  transformer  for  the  lighting  circuits. 

120  to  175  16  C.  P.  incandesent  lamps. 

"In  the  best  practice  the  current  is  brought  aboard  the  dredge 
through  a  cable  composed  of  three  strands  of  insulated  conductor 
well  covered  and  protected  with  jute  and  drawn  through  a  rubber 
hose  for  further  protection  against  water.  Iron-armored  cables 
have  been  tried  but  their  tendency  to  kink,  break  insulation,  and 
burn  in  two,  makes  them  undesirable.  Three  terminal  panels  are 
provided,  one  on  either  side  of  the  rear  of  the  deck-house  and  one 
on  the  bow  gauntree,  for  the  connection  of  the  cable  when  the  dredge 
is  working  on  the  spud  or  on  the  head-line.  From  these  terminals 
the  current  is  carried  through  insulated  conductors  to  the  switch- 
board in  the  pilot-house.  The  switch-board  may  be  subdivided  into 
three  panels,  a  receiving  panel  and  two  distributing  panels.  The 
receiving  panel  is  usually  provided  with  an  oil-switch  and  automatic 


£ 

"a, 
x 

W 


78  DREDGING   FOR   GOLD   IN   CALIFORNIA. 

circuit  breaker  and  with  volt  and  ammeters  of  the  long-scale  type. 
From  this  panel  leads  are  taken  to  one  distributing  panel  and  to 
the  transformers  at  the  full  voltage  of  the  incoming  line,  from  the 
transformers  a  lead  is  carried  to  the  second  distributing  panel  for 
the  lower  voltage  circuits.  Oil-switches  a^e  provided  for  each 
of  the  motor  circuits,  so  that  each  of  the' lines  may  be  cut  out 
separately  in  case  of  accident  to  the  particular  motor  which  it 
supplies. 

"The  motors  'in  use  in  all  three  of  the  districts  named  are  all 
induction  motolrs',  the  direct  current  having  been  found  not  suitable 
for  the  seryice.  There  is  no  doubt  that  the  direct  current  control 
for  variable  speed  motors  is  more  efficient  and  economical  than  the 
rheostatic  control  used  on  the  A.  C.  motors  but  the  severe  service 
and  the  liability  of  stalling  a  motor  at  any  time,  makes  the  D.  C. 
motor  out  of  the  question. 

'Tor  the  variable-speed  dredge-motors,  the  digging  motors 
principally,  use  has  devised  or  caused  to  be  devised,  a  type  of  rheo- 
static control  commonly  known  as  'dredge  resistance'  ;  it  is  the 
ordinary  form  of  grid  resistance,  but  the  amount  of  heat  radiating 
or  dissipating  surface  is  proportioned  so  that  the  motor  may  be 
run  continuously  on  any  notch  of  the  controller  for  a  considerable 
period  of  time. 

"In  the  variable-speed  induction-motors  there  is  of  course  a  great 
loss  of  efficiency  when  running  on  the  lower  notches  of  the  con- 
troller but,  as  the  power  is  comparatively  cheap,  the  actual  monetary 
loss  is  small  in  proportion  to  the  earnings." 

The  winchman  and  controlling  mechanism  may  be  situated  on 
the  main  deck  or  in  a  pilot-house  on  top,  preferably  on  the  starboard 
side,  as  in  this  position,  with  properly  arranged  windows,  he  can 
most  conveniently  see  the  bucket-line,  upper  tumbler,  stacker,  spuds 
or  head-line,  and  side-lines,  and,  at  the  same  time  he  can  manipulate 
the  controlling  levers. 

The  driving  motor  and  pulley,  or  sprocket,  arrangement,  are 
generally  placed  at  the  port  side  forward  of  the  middle  gauntree, 
while  the  winches  are  installed  opposite  on  the  starboard  side  of 
the  boat. 

Various  types  of  gearing  are  used  in  the  main  drive  of  the  upper 
tumbler  and  bucket-line.  The  typical  Risdon  design  has  a  single 
drive-wheel  on  the  starboard  side,  with  the  pinion-bearing  under- 


80 


DREDGING   FOR   GOLD   IN   CALIFORNIA. 


neath,  and  resting  in  a  separate  casting  in  the  middle  gauntree, 
which  in  this  type  of  dredge  is  built  of  iron.  This  has  been 
obviated  in  the  most  recent  machine  of  this  design  (See  description 
of  Bagette  boat  in  Chapter  VIII).  A  sprocket-chain  and  gear-wheel 
are  used  on  a  few  boats,  but  they  do  not  give  the  best  satisfaction. 
A  somewhat  unusual  arrangement  is  the  pentagonal  equalizing  gear 
used  on  the  El  Oro  boat  and  shown  in  Fig.  39,  though  in  the 
figure  the  gear-wheel  has  seven  sides  instead  of  five. 


Fig.  39.     Sprocket-Gear  Driving  Arrangement  on  the  Pennsylvania. 


DREDGING    MACHINES.  81 

The  equalizing  gear  is  designed  to  impart  a  pulsating  motion 
to  the  driving-sprocket  wheel,  exactly  counteracting  the  variations 
in  chain-speed  above  explained.  This  is  accomplished  by  making  the 
pitch-line  of  the  spur-wheel  describe  a  series  of  waves,  the  number  of 
elevations  and  depressions  in  which  correspond  to  the  number  of 
sprockets  on  the  chain-wheel,  and  by  driving  the  spur-wheel  with 
an  eccentric  pinion.  The  sprocket-wheel  and  spur-gear  are  keyed 
on  the  head-shaft  in  proper  relative  positions.  By  the  use  of  this 
gearing  less  power  is  required,  and  the  destructive  strains  due  to 


Fig.  40.     Pentagonal  Equalizing  Gear. 

driving  with  circular  gears  are  eliminated,  thus  permitting  installa- 
tions of  greater  length  or  the  use  of  lighter  chains. 

In  the  usual  modern  driving  arrangements  there  are  two  gear- 
wheels, one  on  each  side  of  the  tumbler  (See  Fig.  41)  and  the 
driving  pinions  are  driven  from  a  counter-shaft  by  pulley-belt  from 
the  motor.  Much  trouble  has  been  occasioned  with  winch-clutches 
and  the  introduction  of  a  thoroughly  satisfactory  clutch  would  be 
much  appreciated.  On  the  Ashburton  at  Folsom  a  magnetic  clutch 
is  used. 

Centrifigual  pumps  are  used  exclusively  on  a  dredge  and  in- 
clude :  The  main  supply  pumps  of  high  and  low  pressure  for  the 
gold-saving  tables,  the  screens,  and  for  discharging  the  buckets; 


•w 


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DREDGING  MACHINES. 


83 


the  sand-pump,  used  to  raise  the  tailing  from  the  well  at  the  stern 
of  the  boat,  to  which  it  is  conducted  when  filling  up  too  fast  behind ; 
and  a  small  pump  for  priming  the  main  pump  and  for  general 
purposes. 

The  method  of  mooring  and  moving  the  boat  is  either  by  spuds 
or  by  head-line.  The  former  are  long  posts,  one  of  which  is 
generally  of  steel  and  the  other  of  wood.  They  are  arranged  in 
guides  at  the  stern  of  the  boat  and  are,  as  a  rule,  24  by  30  in.  in 


Fig.  42.     Wooden  Spud  of  the  Ophir. 

section  and  from  50  to  55  in.  long.  At  Folsom  a  steel  spud  36  by 
42  in.  in  section  is  used.  The  photographs  and  sketches  accompany- 
ing, show  their  design  and  construction.  The  wooden  spud  is 
simply  a  stick  of  Oregon  pine,  shod  at  the  lower  end  with  a  steel 
point  and  fitted  with  sheave-wheels  at  the  upper  end  for  raising  and 
lowering  by  rope.  The  steel  spud  varies  in  section  but  is  usually 
a  box-girder  constructed  of  angles  and  plated  with  wooden  wearing 
surfaces  on  each  side  and  often  with  a  web-plate  in  the  centre.  It 
also  has  a  solid  steel  point  and  sheave-wheels  at  the  top.  In  the 
case  of  one  dredge,  the  Pennsylvania,  two  round  wooden  spuds 


84  DREDGING   FOR    GOLD   IN   CALIFORNIA. 

strapped  with  iron  lengthwise  are  installed,  but  the  boat  is  now 
operated  by  head-line. 

Though  originally  the  dredges  built  by  different  companies 
were  of  distinctive  types,  modifications  have  been  introduced  so 
rapidly  in  one  and  another  design  that  at  the  present  day  it  is 
difficult  to  say  that  any  particular  boat  represents  the  special  design 
of  a  particular  company  as  it  would  be  understood  a  few  years 
ago.  For  instance,  although  dredges  built  by  the  Risdon  company 
still  retain  the  open-connected  bucket-line,  they  have  dropped  the 
cocoa  matting  and  expanded  metal  as  a  gold-saving  appliance  and 
adopted  riffles  and  mercury,  and  in  some  cases  even  tables  and 
launders.  They  have  retained,  however,  in  every  case,  the  trommel 
or  revolving  screen,  and  pan-conveyor ;  in  fact,  the  trommel  is  being 
used  on  many  boats  of  other  makes,  for  example,  the  Nevada,  a 
Bucyrus  dredge ;  and  most  of  the  dredges  on  the  Yuba  have  revolv- 
ing screens  instead  of  shakers.  The  machines  last  mentioned  were 
built  and  designed  by  the  Bucyrus  Co.,  Marion  Steam  Shovel  Co., 
and  the  Boston  Shops.  The  latest  of  these — No.  3,  4,  5,  6,  f,  and 
8 — are- said  to  belong  to  the  Hammon  type  of  dredge,  though  they 
do  not  radically  differ  from  the  Bucyrus  design. 

At  Folsom,  shaking  screens  are  used  on  all  the  boats  except  El 
Dorado  and  at  Oroville  fifteen  boats  have  shaking  screens  while  six- 
teen use  trommels.  The  only  dredges  still  retaining  the  open-con- 
nected bucket-line,  are  eight  Risdon  boats  at  Oroville  and  one  at 
Folsom.*  On  the  Yuba,  No.  I  and  No.  2  dredges  have  shaking 
screens,  but  on  all  the  other  boats,  revolving  trommels  are  installed. 

As  there  are  but  two  dipper  or  shovel  dredges  at  present  work- 
ing in  the  districts  under  consideration,  only  a  few  words  will  be 
devoted  to  them.  The  Garden  Ranch  dredge,  working  about  four 
miles  south  of  Oroville,  is  a  fair  type  of  the  class  and  a  description 
of  it  will  suffice.  The  hull  is  similar  to  the  ordinary  dredge  but 
shorter  than  the  average.  The  power  is  electric  and  only  40  h.  p. 
is  required  to  run  it.  The  digging  apparatus  consists  of  a  hori- 
zontal rotating  table  at  the  bow  to  which  is  attached  an  upright 
crane.  This  is  constructed  of  two  pieces  of  timber,  strengthened 
and  fastened  together  with  iron,  between  which  is  fitted  the  dipper- 
handle.  The  dipper  or  shovel  is  an  iron  box  open  at  the  top,  the 


*Four   Risdon    boats    at    Oroville   and   one   at    Bear   river   have   had   the   bucket   lines 
changed  to  close-connected  buckets,  thereby  increasing  their  digging  capacity  25  per  cent. 


DREDGING  MACHINES. 


85 


bottom  of  which  is  shut  or  opened  at  will  by  a  chain  attachment,  and 
the  top  of  the  front  has  a  toothed  arrangement  for  digging.  The 
capacity  of  the  dipper  is  Ijxj  cu.  yd.  or  36  cu.  ft.  and  the  dredge 
will  dig  about  20,000  cu.  yd.  per  month.  A  hopper  is  attached  out- 
side the  starboard  bow  of  the  dredge  at  the  top,  and  below  this 
the  shaking  screen  is  fitted. 

Seven  side  riffle-tables,  pitching  back  toward  the  centre  of  the 
boat,  empty  into  a  longitudinal  sluice  four  feet  wide  and  running 


Fig.  43.     Broken  Steel  Spud,  Yuba  No.  1. 

the  whole  length  of  the  boat ;  with  the  tail-sluice  emptying  at  the 
stern  as  usual.  The  stacker  is  a  belt-conveyor  running  almost  flat 
over  the  ladder-rollers  and  has  sideboards  attached  to  prevent  the 
belt  slipping  off  the  rollers  and  to  retain  the  material  on  it.  To 
counteract  the  weight  of  the  receiving  hopper,  screens,  stacker,  and 
sluices,  a  hopper  filled  with  rocks  is  placed  on  the  opposite  or  port 
bow  side. 

The  boat  is  held  fast  while  digging  by  three  spuds,  one  at  the 
centre  of  the  stern  and  one  at  each  corner  of  the  bow.  These  are 
all  of  wood,  the  stern  spud  being  strengthened  by  iron  straps  and 


86  DREDGING   FOR    GOLD   IN   CALIFORNIA. 

the  bow  spud  being  held  from  slipping  during  the  dumping  of  the 
dipper  into  the  hopper  by  means  of  a  sort  of  ratchet-gear.  A 
system  of  winches  and  cables  is  used  to  operate  the  crane  and  dipper 
and  centrifugal  pumps  supply  the  water. 

The  method  of  operation  is  as  follows :  The  crane  is  rotated 
to  the  desired  spot  and  the  dipper-handle  is  dropped,  by  the  ratchet- 
gear,  through  the  crane-beams  until  the  dipper  rests  on  the  bottom. 
The  dipper  is  then  caused  to  scrape  along  the  bottom  and  up  the 
bank  in  front,  the  dipper-handle  at  the  same  time  sliding  back 
through  the  crane.  The  dipper  is  raised  directly  over  the  hopper 
and  dumped  by  releasing  the  bottom  opening  with  the  chain  con- 
nection. 

The  crew  consists  of:  One  dredgemaster  (acts  as  blacksmith), 
3  lever-men,  3  crane-men,  3  oilers,  and  1  laborer.  These  are 
employed  on  three  shifts. 

The  single  or  double-lift  dredge,  with  extension-sluice,  sup- 
ported by  a  pontoon,  floating  at  the  stern  of  the  dredge-hull  proper, 
has  gone  entirely  out  of  use  in  the  Sacramento  valley,  though  it 
is  somewhat  doubtful  whether  under  proper  and  careful  manage- 
ment it  is  not  in  many  cases  preferable  as  gold-saver  to  the  present 
stacker  type  of  dredge.  The  Continental  at  Oroville,  which  has 
since  been  re-modeled,  was  a  double-lift  dredge  with  an  extension- 
sluice  as  above.  This  dredge  was  built  in  the  spring  of  1900.  The 
upper  tumbler  was  comparatively  low,  and  the  bucket-line  delivered 
over  a  grizzly  with  bars  6  in.  apart.  The  oversize  went  over- 
board at  a  side  chute,  the  fine  (under  6  in.)  passing  through 
the  grizzly  and  into  a  trommel  with  4-in.  holes.  The  undersize 
from  here  (under  4  in.)  dropped  into  a  sump  in  the  hull  of 
the  boat  from  where  it  was  raised  by  a  huge  centrifugal  pump  into 
the  long  sluice,  supported  by  a  pontoon  at  the  rear. 

With  the  single-lift  dredge  the  material  after  passing  over 
the  screen  is  delivered  directly  into  the  long  sluice,  thus  obviating 
the  pumping  expense.  At  Alder  Gulch,  in  Montana,  two  single-lift 
sluice  dredges,  such  as  above,  have  been  working  successfully  for 
several  years  under  the  most  adverse  climatic  conditions,  and  now, 
a  12  cu.  ft.  bucket  dredge  with  hull  130  by  48  ft.  is  being  built. 


Fig.  44.     Well  of  Yuba  No.    8,    showing  Upper  Tumbler,    Hopper  Grizzly, 
Idler,  and  Save-All  Sluices  before  Installation  of  Bucket-Line. 


IV.    OPERATION. 


The  system  of  operation  is  as  follows :  The  material  is  dug 
by  the  buckets,  elevated  and  dumped  into  the  hopper  at  the  top, 
from  whence  it  is  fed  to  the  screens.  The  oversize  escapes  from  the 
screen  and  falls  into  a  small  chute  at  the  end  which  delivers  it  to 
the  conveyor  to  be  carried  aft  to  such  a  distance  that  it  will  not  be 
in  the  way.  The  fine  material  passing  through  the  screen  is  taken 
by  the  water  of  the  washing  jets  over  the  gold-saving  tables ;  the 


Fig.  45. 

tailing  is  carried  by  a  suitable  sluice  far  enough  astern  to  prevent  its 
interfering  with  the  future  operation  of  the  boat.  Should  it  inter- 
fere by  flowing  too  close  about  the  stern,  the  tailing  is  carried  to  a 
well  at  the  end  of  the  hull  to  be  lifted  by  the  sand-pump  to  the  far 
side  of  the  tailing-pile.  As  mentioned  before,  the  two  methods  of 
working  the  boats  are  by  spuds  and  head-line  and  in  the  following 
description  it  is  attempted,  assisted  by  the  use  of  sketches,  to  make 


OPERATION. 


89 


clear  these  methods  and  the  conditions  under  which  each  is  appli- 
cable in  both  methods  of  operating.  Side-lines  are  used  to  move  the 
boat  across  the  pond;  these  are  anchored  in  the  manner  shown  in 
Fig.  45  either  by  'dead-men',  or  to  any  natural  object  such  as  a 
tree,  etc.,  and  pass  from  these  anchors  through  sheaves  on  the  for- 
ward deck  and  on  the  bucket-ladder  of  the  boat,  thence  back  to 
the  winch-drum.  By  winding  or  unwinding  the  rope  on  the  drum, 


j-///. 


TS//C/C. 

Fig.  45^2.     Cross-Section  of  Steel  Spud. 

the  boat  is  passed  to  right  or  left  as  desired.  In  using  the 
'dead-man'  method  of  anchoring,  a  T-shaped  trench  is  dug,  about 
4  ft.  deep  in  that  portion  which  represents  the  cross  of  the 
T  and  the  part  that  represents  the  upright  of  the  T  slopes  from  the 
surface  down  to  the  cross  part.  A  piece  of  wire-rope  is  firmly 
attached  to  a  log  placed  in  the  bottom  of  the  cross  trench  and  a  loop 
is  made  at  the  surface  end;  to  this  is  attached  the  land^end  of  the 
head-line  or  side-line.  Planks  are  driven  down  in  front  of  the  log 
and  the  earth  is  filled  in  and  tamped ;  several  of  these  are  placed  at 


90 


DREDGING   FOR    GOLD   IN   CALIFORNIA. 


convenient  distances  from  the  pond.  Chinese  are  usually  em- 
ployed for  this  purpose  as  well  as  in  removing  trees,  stumps,  etc., 
and  in  generally  preparing  the  ground  in  front  of  the  dredge. 

The  head-line  is  attached  to  the  bank  similarly  to  the  side-lines 
but  to  a  different  winch-drum  on  the  boat,  which  is  moved  backward 


Fig.  46.     Method  of  Anchoring  a  'Dead-Man'. 

and  forward  by  winding  and  unwinding.  The  No.  4  boat  of  the 
Folsom  Development  Co.  (13  cu.  ft.  buckets)  has  three  of  these 
anchorages  placed  a  long  distance  in  front  of  the  boat  and  the  head- 
line is  fastened  to  each  in  turn  as  the  boat  is  moved  across  the  cut 
by  the  side-lines.  Side-lines  vary  from  %  to  1  in.  diam.  and 
head-lines  from  ll/\.  to  \l/2  in.  diam.  With  a  head-line,  the  digging- 


Fig.  47  and  Fig.  48. 


ladder  is  kept  at  the  bottom  of  the  digging- face  and  the  tendency  is 
to  under-cut  the  bank  and  allow  it  to  cave  to  the  buckets,  see  Fig.  48. 
This  is  done  by  making  short  vertical  cuts  of  about  5  ft.  in  height 
across  the  bottom  of  the  pond.  Some  of  the  material  that  caves  falls 
over  the  sides  of  the  buckets,  but  as  these  dig  and  scrape  up  the 


OPERATION. 


91 


ground  for  about  20  ft.  behind  the  lower  tumblers  this  caved  por- 
tion is  usually  collected.  Operation  by  head-line  is  best  adapted 
for  soft  ground. 

When  the  gravel  is  toughly  cemented  and  the  digging  is  hard, 
spuds  are  advisable.      The   method  of  using  them  is   as   follows : 


Fig.  49.     Chinaman  Removing  Trees  in  Front  of  a  Dredge. 

The  digging-face  of  the  pit,  as  in  the  case,  of  a  head-line  boat  as 
well,  is  kept  from  150  to  250  ft.  wide,  and  the  boat  is  passed  from 
side  to  side  by  the  side-lines.  The  bank  is  cut  in  terrace  or  sloping 
shape  as  in  Fig.  47.  Movement  forward  and  backward  is  effected 
by  first  winding  up  on  the  starboard  side-line,  when  the  boat  will 
assume  the  positions  shown  in  Fig.  51.  This  is  called  stepping  or 
'walking'  the  boat  ahead.  Care  must  be  exercised  in  moving  the 


92 


DREDGING   FOR    GOLD   IN   CALIFORNIA. 


boat  with  spuds  not  to  place  each  new  pivotal  point  so  that  the 
stacker  will  cover  valuable  ground  to  be  dredged  on  the  return  cut 
or  fill  such  portion  of  the  pond  as  will  tend  to  ground  the  hull  when 
changing  its  position.  Sometimes  the  dredging  is  done  in  a  direc- 
tion following  or  crossing  a  right-of-way  stream  or  an  irrigation 
ditch  and  the  ingenuity  of  the  dredge-master  is  taxed  in  keeping 
the  channel  open  behind  him,  through,  or  to  one  side  of  his  stack- 
pile. 


Fig.  50.    Removing  Stumps  along  Irrigation  Ditch  in  Front  of  the  Nevada. 

The  advantages  and  disadvantages  of  spuds  as  compared  to 
head-lines  are  as  follows :  Spuds  cause  more  loss  of  time  in 
moving,  and  the  stacking  problem*  is  rendered  difficult,  but  harder 
ground  may  be  dug  with  less  ramming  of  the  bank ;  the  ground  may 
be  dug  cleaner,  and  with  an  uneven  surface  spuds  are  preferable. 
The  surging  of  the  head-line  and  the  ramming  of  the  bank  are 
most  objectionable  features,  particularly  in  hard  ground  or  with 
open-connected  bucket-lines,  and  there  is  probably  more  loss  of  gold 
from  caved  material.  On  the  other  hand,  the  loss  of  time  is  less 
and  stacking  is  easier. 


*I  can  see  no  reason  why  this  should  not  be  facilitated  very  greatly  by  using  a 
swinging  stacker  pivoted  at  the  lower  end.  This  is  the  method  used  in  sluice  practice 
at  Ruby,  Montana,  and  at  the  Ashburton  dredge  at  Fair  Oaks,  California. 


k 


s 


OPERATION. 


95 


A  number  of  boats  nowadays  are  equipped  with  both  head-line 
and  spud,  and  either  can  be  used  under  different  conditions.  With 
the  use  of  spuds  the  plan  of  the  digging-face  is  in  arc-form,  the 


Fig.  53.     Tail  Sluices  and  Spuds  on  Yuba  No.  7.    Steel  Spud  (on  the  Right) 
Down;  Wooden  Spud  Up. 

boa-t  being  swung  from  one  side  of  the  cut  to  the  other  in  carrying 
forward  the  excavation.  The  whole  width  of  the  cut  in  alternate 
sections  is  usually  carried  forward  to  the  limit  of  the  property  and 
the  dredge  is  turned  round  and  in  returning  it  makes  a  similar  cut 


96  DREDGING   FOR   GOLD   IN   CALIFORNIA. 

alongside  the  first,  but  advancing  in  an  opposite  direction. 
When  a  dredge  is  completed  and  ready  for  work  it  sometimes 
happens  that  it  is  some  distance  from  its  place  of  operation. 
In  such  a  case  it  becomes  necessary  to  dig  to  the  dredging 
ground.  As  shallow  a  trench  is  dug  as  will  float  the  hull  and 
occasionally  the  curious  sight  is  seen  of  several  boats  at  differ- 
ent elevations  climbing  or  descending  a  slope  formed  by  the 
river  benches  and  carrying  their  own  ponds  along  with  them. 
The  water  for  the  ponds  is  either  supplied  from  the  system 
of  irrigation  ditches  or  it  is  pumped  into  the  pond  from  the 
river  or  some  other  source.  The  buckets  are  designed  in 
shape  so  that  they  will  best  carry  the  material  at  the  greatest 
angle  at  which  the  ladder  digs,  which  in  general  practice  is 
not  over  45  degrees. 

When  the  pond  is  below  the  river,  or  where  the  condition  is 
such  that  the  permanent  water-level  renders  the  depth  too  great  for 
the  capacity  of  the  dredge,  certain  expedients  must  be  resorted  to. 
If  the  gold  is  at  a  depth  only  a  few  feet  greater  than  the  capacity  of 
the  dredge,  pumping  is  resorted  to  and  the  surface  lowered  sufficiently 
to  allow  the  auriferous  gravel  to  be  reached  by  the  ladder. 
Lengthening  the  ladder  and  bucket-line  is  the  expedient  used 
on  the  Yuba  and  some  of  these  boats  are  now  digging  to  a 
depth  of  64  ft.  below  water-level.  A  somewhat  novel  and  at 
the  same  time  successful  method  has  been  introduced  in  the 
case  of  the  No.  5  boat  of  the  Folsom  Development  Co.  This 
dredge  is  working  on  a  high  bank  several  hundred  feet  above 
the  bench-gravels  of  the  American  river  and  the  pay-dirt  con- 
tinues to  a  depth  of  60  ft.  below  the  surface  of  the  ground. 
By  discharging  with  pumps  and  (when  necessary)  filling  the 
ponds  by  the  use  of  irrigation  ditches,  the  level  of  the  water 
is  kept  as  nearly  as  possible  at  a  constant  depth  of  about  35  ft. 
A  bank  of  about  25  ft.  is  therefore  left  in  front  and  above  the 
boat.  This  is  caved  by  the  use  of  a  'monitor'  from  the  boat 
supplied  by  a  centrifugal  pump  with  a  capacity  of  400  gal. 
per  min.  (See  Fig.  54.)  The  scheme  works  well  and  obviates 
the  long  ladder  and  bucket-line. 

The  stacker  is  longer  than  usual  on  this  boat,  but  as  the 
sand-pump  had  to  be  in  use  almost  constantly,  a  device  con- 
sisting of  an  elevator-belt  with  small  buckets  attached  was 


PQ 
"So 

5 

be 


98  DREDGING   FOR   GOLD   IN   CALIFORNIA. 

arranged  experimentally  to  lift  automatically  from  the  sand- 
well  into  the  stacker-belt.  It  was  found  that  so  much  extra 
water  tended  to  sluice  the  material  in  the  belt  back  into  the 
boat  so  that  now  the  experimental  belt  is  to  be  carried  up 
higher,  to  empty  into  a  launder  that  will  deliver  onto  the  stack- 
pile.  When  the  gravel  proves  excessively  hard  in  front  of 
the  dredge  and  is  composed  of  the  so-called  'cemented  ground', 
blasting  is  often  employed  to  facilitate  the  work.  Examples 
of  this  work  are  given  below. 


Fig.  55.     Sand  Pump  Working  on  Yuba  No.  7. 

In  one  case  the  dredging  pond  was  150  ft.  wide;  at  25  ft. 
from  the  face  rows  of  holes  were  drilled  6  in.  diam,  at  50  one 
foot  intervals  and  cased  in  the  usual  manner.  Cartridges 
made  of  sections  of  5-in.  stove-pipe  filled  with  No.  2  giant 
powder  were  used  and  a  cap  put  on  each  end  and  the  cylinder 
covered  with  gear  grease;  this  was  lowered  into  the  holes,  the 
casing  withdrawn  and  the  charges  fired  simultaneously  by 
electricity,  35  Ib.  of  powder  being  used  per  hole.  In  another 
case,  at  Oroville,  where  the  depth  of  dredging  ground  was 


OPERATION.  99 

35  ft.,  a  row  of  holes  was  put  down  at  30  ft.  from  the  face  at 
40  ft.  apart ;  these  were  drilled  to  a  depth  of  30  ft.  each  and 
the  charge  (100  Ib.  of  40%  dynamite  per  hole)  was  inserted 
in  the  same  manner  as  above,  the  blasts  being  fired  by  fuse. 
The  cost  of  this  work  added  4c.  per  yd.  to  the  total  cost  of 
dredging.  In  a  third  instance,  the  holes  were  drilled  to  within 
15  ft.  of  the  so-called  bedrock  (volcanic  ash)  and  charged  with 
125  Ib.  of  dynamite  per  hole  and  fired  simultaneously  by  battery. 
The  extra  cost  per  yard  was  2  to  2l/2  cents. 

Most  companies  have  a  regular  system  of  laying  out  their 
property  for  dredging  and  the  reports  from  the  foreman,  winch- 
man,  and  superintendent  are  often  elaborate.  The  Oro  Water, 
Light  &  Power  Co.  uses  a  useful  and  simple  method,  the  par- 
ticulars of  which  were  given  to  me  by  Karl  Krug,  engineer  and 
manager  of  the  company.  The  property  to  be  worked  is  laid 
off  in  50-ft.  squares  and  stakes  are  placed  at  each  corner. 
The  lines  crossing  the  property  are  lettered  A,  B,  C,  etc.,  while 
those  running  up  and  down  are  numbered  50,  100,  150,  etc., 
and  the  stakes  at  the  corner  are  marked  to  correspond  A  50, 
A  100,  B  50,  B  100,  etc.,  etc.  Spuds  are  used,  and  the  method 
followed  is  to  step  ahead  10  ft.,  when  the  ground  is  soft  and 
about  7  ft.  when  hard.  A  cut  100  ft.  wide  is  carried 
across  in  a  circular  sweep  from  one  to  several  feet  in  depth, 
also  depending  upon  whether  the  ground  is  hard  or  soft.  When 
a  distance  of  50  ft.  ahead  has  been  dug  in  this  way,  the  boat 
is  backed  and  moved  across  and  100  ft.  ahead  is  done,  alongside 
the  first  cut,  the  face  of  the  latter  then  being  50  ft.  ahead  of 
the  former.  The  boat  is  then  backed  again  and  moved  across 
to  the  first  cut,  and  each  cut  100  ft.  wide  is  carried  on  50  ft. 
ahead  of  the  one  alongside  of  it,  so  that  when  the  boundary 
of  the  property  has  been  reached  a  strip  200  ft.  wide  has  been 
dug  the  whole  length  or  width  as  the  case  may  be.  Appended 
are  a  plan  (Fig.  56)  and  a  report,  both  of  which  refer  to  a 
24  hr.  run  of  the  Lava  Beds  No.  3  and  show  exactly  how  the 
records  are  kept  on  the  dredges  of  this  company. 

Referring  to  these  figures  and  assuming  that  winchman  No.  1 
comes  on  shift  at  8:30  a.  m.,  5  min.  are  occupied  in  step- 
ping ahead.  During  his  shift  he  advances  along  the  zero  line 
of  the  starboard  side  of  the  cut  11  ft.  and  at  the  port  side  along 


100 


DREDGING   FOR   GOLD   IN   CALIFORNIA. 


the  150  ft.  line,  10  ft.  The  width  of  the  swing  on  bedrock  i 
always  kept  up  to  the  even  hundred  lines  while  the  excavate* 
surface  measurement  depends  upon  the  amount  of  caving.  Thes 
details  are  recorded  in  the  small  table  at  the  upper  left  han< 
corner  of  the  report,  as  are  also  the  depths  and  heights  of  th 
bank.  From  these  records  his  cubic  yardage  per  hour  may  b 
quickly  arrived  at.  This  is  generally  obtained  from  the  sketcl 
by  polar  planimeter. 


0-200 


0-/5O 


Fig.  56. 

Winchman  No.  2  comes  at  5  :28,  and  No.  3  at  3  :06,  as  show 
by  the  report;  their  work  being  shown  in  a  similar  manner  t 
No.  1's  work.  The  loss  of  time  and  cause  of  it  are  also  show 
on  this  report  and  in  this  case  only  amounted  to  47  min.  i 
the  24  hr. — less  than  4% — which  of  course,  is  much  less  tha 


II1 


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6 

3 


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II     I 


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102          DREDGING   FOR    GOLD   IN   CALIFORNIA. 

the  average.  The  winchman's  report  is  checked  by  the  oiler, 
dredgemaster,  master-mechanic,  and  the  manager,  before  it  goes 
to  the  head  office.  As  it  is  well  known  how  much  the  winch- 
man's capacity  is,  he  has  to  account  for  undue  lost  time  in  case 
his  work  does  not  come  up  to  the  average. 

By  referring  to  the  records  of  drill-holes  contained  in  the 
chapter  on  Prospecting,  it  will  be  seen  that  the  gold  lies  in  a  most 
irregular  manner  throughout  the  deposits.  It  occasionally  hap- 
pens, however,  that  it  is  contained  over  a  certain  well-defined  area 
in  a  streak  near  the  bottom  or  it  is  definitely  known  that  a  certain 
thickness  at  the  top  is  barren.  In  such  cases  arrangements  are 
made  to  prevent  wear  on  the  tables  and  sluices  by  'blanking'  the 
screens. 

On  the  Butte,  while  changing  the  boat  from  one  point  to 
another  across  barren  ground  where  only  'flotation'  depth  was 
being  dug,  unperforated  plates  were  bolted  on  top  of  the  shaking 
screens.  On  the  Pennsylvania,  two  steel  plates,  like  hatches,  were 
hinged  on  each  side  of  the  screen,  and  at  another  time  on  the  same 
boat,  the  material  was  prevented  from  delivery  into  the  screen ; 
everything  was  dumped  into  the  well;  but  this  practice  had  to  be 
discontinued  on  account  of  the  rapid  filling  of  the  pond.  On  the 
Yuba,  when  digging  unproductive  material,  the  water  was  shut 
off  and  very  little  stuff  came  through  the  trommels. 

Respecting  the  relative  merits  of  open  and  close-connected 
bucket-lines  it  has  been  thoroughly  proved  that  at  Oroville,  Fol- 
som,  and  on  the  Yuba,  close-connected  buckets  may  be  used  with- 
out any  serious  hindrance  from  operating  causes,  and  therefore, 
it  is  folly  to  use  an  open  connection,  which  may  have  its  advan- 
tages in  other  localities.  One  of  the  older  boats  during  the  past 
year  at  Oroville  changed  from  an  open  to  a  close-connected  line 
and  increased  its  monthly  yardage  from  45,000  to  60,000  cu.  yd. 
per  month.  Moreover,  in  practice,  other  conditions  being  normal, 
an  open  line  of  buckets  will  only  empty  at  the  rate  of  from  12 
to  13  per  min.,  while  a  close-connected  line  empties  at  the  rate 
of  from  19  to  22  per  min.  As  far  as  the  relative  filling  capacity 
is  concerned,  under  ordinary  conditions  and  with  a  proper  arrange- 
ment, there  is  apparently  little  difference  between  them.  A 
somewhat  common  accident  regarding  bucket-lines  occurs  when 
they  slip  over  the  cheek  of  the  lower  tumbler.  A  method  of 


OPERATION. 


103 


replacing  the  bucket-line  when  only  partly  off  is  as  follows: 
Blocks  of  wood  or  sticks  of  cordwood  are  inserted  between  the 
ladder-frame  and  the  bucket-line  just  above  the  cheek  of  the  tum- 
bler on  the  side  on  which  it  happens  to  be  off.  The  upper  tum- 
bler is  then  reversed  and  the  chain  of  buckets  backed  slowly  and 
carefully  down.  As  each  piece  of  wood  is  carried  round  the 
lower  tumbler,  new  pieces  are  inserted  above,  and  the  line  is 
thus  gradually  worked  on.  When  almost  or  entirely  off  the 


Fig.  57.     Bucket-Line  Laid  Out  on  Shore  Ready  for  Installation 
on  the  Yuba  No.  8. 

lower  tumbler,  the  ladder, is  raised  and  a  piece  of  steel  shafting 
is  poked  under  the  bucket-line  and  on  top  of  the  ladder  as  close 
as  possible  above  the  cheek  of  the  lower  tumbler  on  the  side  that 
the  bucket-line  is  off  and  in  a  direction  diagonally  toward  the 
cheek  on  the  opposite  side.  It  is  then  lashed  to  the  cheek  and 
the  bucket-line  backed  down  as  before. 

On  the  Yuba  I  saw  a  more  extraordinary  case  than  either 
of  those  just  explained.  At  No.  2  dredge  for  some  unaccountable 
reason,  after  the  bucket-line  came  off  the  lower  tumbler,  winching 


104 


DREDGING   FOR    GOLD   IN   CALIFORNIA. 


was  continued  for  some  time  and  two  of  the  ladder-hangers  were 
carried   away   before   the   motive   power   was   shut   off.       By  that 


Fig.  58.     Accident  to  Bucket-  Line  on  Yuba  No.  2. 

time  the  bucket-line  was  hanging  over  one  side  of  the  ladder  and 
in  the  well  of  the  boat.  The  line  was  uncoupled  as  near  the 
lower  tumbler  as  possible  and  the  lower  end  made  fast  to  a 


OPERATION. 


105 


crucible-steel  cable  \Y\  in.  diam.,  kept  for  just  such  an 
occasion.  The  line  was  rotated  in  the  same  direction  as  when 
digging,  the  lower  end  at  the  same  time  being  drawn  out 
on  the  bank.  On  emerging  from  the  water  a  most  extraordinary 
condition  was  observed.  The  heavy  chain  of  ungainly  buckets, 
each  weighing  probably  over  1500  lb.,  was  twisted  into  a  perfect 
loop,  the  actual  circle  or  loop  being  completed  in  eight  buckets. 
Fourteen  buckets  containing  the  offending  loop  were  detached 
and  hung  up  as  shown  in  Fig  58,  and  after  taking  them  apart 


Fig.  59.     Cable  Transport  by  Board  Trestles. 

the  line  was  straightened  out  on  the  bank,  put  together,  and  made 
fast  to  the  portion  on  the  ladder.  The  upper  tumbler  was  then 
rotated  and  the  line  coupled.  The  accident  happened  at  6:30 
on  Friday,  June  8,  and  the  boat  resumed  digging  on  the  following 
Monday  afternoon. 

A  more  important  consideration  than  one  might  suppose  is 
the  necessity  for  keeping  the  boats  scrupulously  clean.  This  is 
applicable,  of  course,  to  all  machinery,  but  there  is  so  much  mud, 
water,  and  grease  in  the  confined  space  upon  a  dredge,  that  it 
becomes  a  most  important  factor  in  its  life  and  serviceable  work. 


106 


DREDGING   FOR    GOLD   IN   CALIFORNIA. 


Besides,   it  costs  little  to  effect  this.      Two  of  the  boats   in  par- 
ticular at  Oroville  are  noticeable  for  this  characteristic  and  both 


Fig.  60.     Cable  Transport  by  Barrel  Pontoons. 

the  boats  and  parts  are  kept  constantly  washed  down  with  a 
hose  and  at  intervals  they  are  painted,  etc.  Care  is  taken  to  cover 
grease-leaks  so  that  the  amalgamation  will  not  be  effected  and 


OPERATION. 


107 


receptacles  are  placed  to  catch  the  drip,  etc.  On  one  of  the  Yuba 
boats  the  same  care  is  conspicuous  and  a  large  sign  hung  in  a 
prominent  place  carries  out  the  idea: 


OUR  MOTTO  : 

A  PLACE  FOR  EVERYTHING  AND 
EVERYTHING  IN  ITS  PLACE. 


The  contrast,  however,  between  this  boat  and  some  of  its  neigh- 


Fig.  61.     Cable  Transport  by  Forward  Gauntree. 

bors  was  partly  due  to  the  small  amount  of  clay  that  it  had  to 
contend  with. 


108         DREDGING   FOR   GOLD   IN   CALIFORNIA. 

The  insulated  cables  that  transmit  the  electric  current  to 
the  dredges  from  the  sub-stations  are  generally  of  the  submarine 
armored  type  and  as  immersion  in  water  for  any  length  of  time 
is  bound  to  have,  either  directly  or  indirectly,  an  injurious  effect 
upon  these,  several  methods  are  employed  by  which  they  are  con- 
veyed across  the  ponds.  At  the  Nevada,  ordinary  floats  made 
of  boards  in  the  shape  of  small  cross-trees  are  used  while  at  the 
Butte  pontoons  made  of  barrels  are  employed  and  appear  to  answer 
the  purpose  well.  The  Leggett  No.  3  suspends  its  cable  by  means 
of  a  hanger  from  the  forward  gauntree  frame  but  it  is  contended 
that  the  jarring  from  the  digging-ladder  is  transmitted  more 
directly  to  the  cable  in  this  manner  and  has  an  injurious  effect  on 
it.  "The  best  method  that  I  observed  is  that  now  used  at  Folsom, 
where  the  cable  is  passed  through  rubber  hose  and  effectually 
protected  from  water. 


V.   THE   METALLURGY    OF   DREDGING. 

The  gold-saving  appliances  of  a  dredge  consist  respectively 
of  screens,  tables,  and  sluices. 

The  essential  duty  of  the  screen  is  to  classify  the  material 
prior  to  concentration,  it  also  serves  to  disintegrate  or  break  up 
the  material  passing  over  or  through  it,  so  that  particles  of  gold 
may  not  be  carried  off  in  lumps  of  clay  or  cemented  gravel,  to 
be  lost  by  passing  out  at  the  lower  end  over  the  stacker.  The 
aim  also,  of  course,  is  to  prevent  the  larger  gravel  and  boulders 
from  being  washed  over  the  sluices.  It  is  held  by  some  authorities 
that  the  old  fashioned  single-lift  dredge,  where  everything  passed 
from  the  upper  tumbler  over  long  sluice-boxes  with  riffles  sup- 
ported on  a  pontoon  behind  the  dredge,  is  of  equal  gold-saving 
efficiency  and  more  economical  (when  properly  designed  and  man- 
aged) than  the  present  style.  There  are  cases  too  where  the 
double-lift  dredge  with  the  long  sluice  might  be  advantageously 
replaced  by  the  single-lift  pattern.  As  to  the  choice  between 
the  revolving  trommel  and  the  shaking  screen,  those  who  use  the 
former  claim  that  when  constructed,  as  it  usually  is,  with  flanges 
and  rods  across  it,  it  turns  over  lumps  and  exposes  them  to  the 
action  of  the  water-jets  on  all  sides.  On  the  contrary,  those  who 
advocate  the  shaking  screen  contend  that  the  jets  have  a  thinner 
surface  to  play  upon,  the  actual  screening  is  larger  and  the 
material  is  deposited  on  a  wider  surface.  From  the  modern 
standpoint,  however,  the  last  consideration  does  not  count  for 
much. 

The  first  cost  and  repairs  of  the  revolving  screen  are  usually 
greater  than  those  of  the  shaking  type.  The  diameter  of  the 
holes  is  governed  by  the  size  of  the  gold ;  as  this  is  usually  very 
fine  throughout  the  Sacramento  valley,  the  holes  vary  from  T\  in. 
to  Y-2  in.  at  the  upper  part  of  the  screen  and  from  y2  to  ^  in.  at 
the  lower  end.  The  holes  are  reamed  on  the  outer  side  to  give  a 
free  discharge.  Anyone  who  has  watched  the  action  of  either  sort 
of  screen  for  any  length  of  time,  particularly  on  boats  where  a 
sticky  clay  is  treated,  does  not  have  to  be  told  that  neither  of  them 


110 


DREDGING   FOR    GOLD   IN   CALIFORNIA. 


is  a  thoroughly  efficient  machine  for  the  work.     Quantities  of  fine 
material  may  be  seen  passing  to  the  stack-piles. 

The  patterns  of  the  gold-saving  tables  and  sluices  differ 
widely.  Formerly,  on  the  Risdon  boats,  cocoa  matting  with  ex- 
panded metal  in  diamond-mesh  pattern  was  used,  but  this  material 
has  been  almost  exclusively  replaced  by  riffles  and  quicksilver, 
but  the  designers  still  use  the  tables  sloping  toward  each  side  of 
the  boat  at  right  angles  to  the  slope  of  the  screen.  In  boats  o\ 
modern  design  various  devices  are  used  under  the  screens. 


Fig.  62.     Tail  Sluice,  showing  both  Angle-Iron  Riffles  and  Cocoa 
Matting  with  Expanded  Metal. 

A  certain  proportion  of  the  material  delivered  by  the  bucket 
over  the  upper  tumbler  does  not  go  into  the  screen-hopper,  being 
carried  too  far  forward  in  its  delivery.  A  grizzly  is  therefore 
arranged  at  the  edge  of  the  well ;  the  undersize  falls  onto  a  short 
sluice  with  riffles  (sometimes  two  are  used,  one  under  the  other 
and  sloping  in  opposite  directions),  which  either  empties  directly 
into  the  well  or  (when  sloping  toward  the  stern)  delivers  into 
a  pipe  passing  through  the  deck,  or  it  may  be  carried  down  the 
entire  length  under  the  screen  to  the  stern  of  the  boat.  On  the 
Yuba  boats  where  deep  gravel  is  encountered  and  long  ladders 


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112          DREDGING   FOR    GOLD   IN   CALIFORNIA. 

are  used,  the  tendency  of  the  sag  of  the  bucket-chain  is  to  scrape 
against  the  edge  of  the  well.  An  idler  (a  large  flanged  wheel 
or  drum),  is  installed  beneath  the  upper  tumbler  and  serves  to 
take  up  this  sag.  Although  'save-all'  sluices  have  been  placed 
on  these  boats,  they  are  not  of  much  service.  In  most  cases  on 
the  Yuba  the  riffles  are  either  banked  with  sand  or  carried  away 
altogether  by  falling  boulders  from  the  overflow  of  the  screen- 


Fig.  64.     Clean-Up  Apparatus  and  Riffles  on  the  Butte.    (a)  Pot.    (b)  Strainer. 

(c)  Scoop,     (d)  Pan.     (e)  Riffles  and  Mercury  Surface. 

(f)  Appel's  Mercury  Surface. 

hopper.  This  is  to  be  obviated  by  placing  riffle-bars  between  the 
flanges  of  the  idler-drum.  Various  gold-saving  devices  are  used 
on  the  tables  and  sluices,  but  the  angle-iron  riffle  is  the  most 
popular.  This  may  be  placed  across  the  sluice-box  or  lengthwise, 
with  small  stones  between  the  bars;  a  combination  of  these  two 
is  often  used.  Quicksilver,  of  course,  is  placed  behind  the  riffles 
and  at  intervals,  near  the  head  of  the  tables  there  is  a  mercury 
trap  of  variable  design.  The  best  I  saw  and  that  giving  the 
largest  and  cleanest  surface  was  one  designed  by  Mr.  Harrison 


Ffe.  65. 


114          DREDGING   FOR    GOLD   IX   CALIFORNIA. 

Appel,  at  Oroville,  and  used  on  the  Bnttc  and  El  Oro  dredges.  It 
is  made  of  wood  with  thin  strips  of  metal  on  edge  placed  at  in- 
tervals of  y2  in.  apart.  Small  blocks  of  wood  keep  the  strips 
separate. 

The  chief  value  of  cocoa  matting  is  as  a  collector  of  fine 
gold,  but  the  accumulation  of  sand  and  slime  interferes,  so  that 
in  the  clean-up  often  only  the  coarse  gold  that  settles  behind  the 
metal  is  recovered.  It  is  a  good  idea  to  use  a  piece  of  this 
material  near  the  foot  of  the  plates,  and  indeed,  some  experiments 
are  being  made  in  this  direction  at  the  present  time. 

To  illustrate  some  of  the  different  screening  and  gold-saving 
arrangements  on  the  various  boats,  the  following  specific  cases 
are  described  by  means  of  rough  sketches.  As  an  example  of 
the  simpler  modern  boat,  the  Yuba  No.  _/  has  the  arrangement 
shown  in  Fig.  65.  Eight  tables  sloping  at  right  angles  to  the 
revolving  screen  empty  into  a  longitudinal  sluice  called  the  stream- 
down  box ;  this  is  parallel  to  the  screen.  The  tables  and  sluice 
are  fitted  with  wooden  riffles  topped  with  iron  bands,  placed  as 
shown  in  detail  sketches.  The  bars  are  1  in.  high  and  1 
in.  wide,  and  the  spaces  between  are  1  in.  wide;  the 
tables  are  30  in.  wide  and  the  'stream-down  sluice'  is  18  in. 
wide  at  top,  4  ft.  3  in.  wide  at  the  tail  and  30  ft.  long.  A  plain 
iron  sluice  extension  without  riffles  carries  off  the  tailing. 

A  similar  arrangement  is  used  on  the  Boston  &  California 
No.  3  and  other  boats.  More  complicated  schemes  are  employed 
on  the  Pennsylvania  at  Oroville,  built  by  the  Miners'  Iron  Works, 
of  San  Francisco,  and  the  Biggs  No.  2  (now  Exploration  No.  2) 
built  by  the  Bucyrus  company.  In  the  first  case  two  flat  shaking-, 
screens  are  installed  one  over  the  other,  with  opposite  motion. 
The  upper  screen  has  holes  y2  in.  diam.,  and  the  holes  in  the  lower 
screen  are  ^\  in.  at  the  upper  end  and  y%  in.  at  the  lower.  Under 
the  lower  screen  are  six  layers  of  plank  (ten  in  each  of  the  two  upper 
layers  and  nine  in  each  of  the  others)  placed  across  the  direction  of 
the  slope  of  screens,  at  intervals,  the  layers  sloping  alternately  for- 
ward and  aft.  These  planks  are  grooved  lengthwise  with  blocks 
placed  in  the  grooves  at  intervals ;  they  break  joint  in  alternate 
grooves  and  are  drawn  out  at  clean-up.  This  forms  a  mercury 
trough.  Under  the  layers  of  plank  are  ten  tables  sloping  at  right 
angles  to  slope  of  screens,  each  about  18  in.  wide  and  fitted  with 


THE  METALLURGY   OF  DREDGING. 


115 


amalgamating  surfaces,  planks  are  placed  cross-wise  with  1  in. 
diam.  holes  bored  in  them,  cocoa  matting,  and  cross-riffles.  These 
empty  into  a  'stream-down  box'  with  cross-riffles  and  end-riffles  at 


ELEMT/OH. 


S£C7VO/V. 

Fig.  66.     Tables  on  the  Pennsylvania. 

the  lower  sections.      The  side  tables  have  two  drops  between  the 
screen  and  stream-down  sluice. 

The  Biggs  No.  2  has  a  single  shaking  screen.      Under  this 
are   two   layers   of   plank  placed   cross-wise   and   extending  about 


116 


DREDGING   FOR    GOLD   IN   CALIFORNIA. 


half  way  from  the  top  of  the  screen  toward  the  centre.  The  ma- 
jority of  these  are  fitted  with  small  cross-riffles.  Below  (See  Fig. 
67)  are  the  riffle  tables  and  stream-down  box,  similar  to  those  on 
the  Yuba  No.  4  (See  Fig.  65). 


Fig.  67. 

On  the  Leggett  No.  3,  a  Risdon  boat  built  in  1904  at  Oroville, 
the  arrangement  is  somewhat  different  (See  Fig.  68).  A  revolv- 
ing trommel  54  in.  diam.  is  used,  built  in  four  sections  lengthwise. 
The  total  length  of  screening  surface  is  14  ft.  The  holes  in  the 
three  upper  sections  are  y$  in.  diam.  and  the  lower 


THE  METALLURGY   OF  DREDGING. 


section  has  l/2  in.  holes.  There  is  one  row  of  square  holes 
two  inches  around  the  top,  to  allow  small  stones  to  come 
through  for  filling  riffle-spaces.  The  purpose  of  these  stones 
is  to  protrude  above  the  riffles  and  stir  up  the  sand  as  it  passes, 


0/23 


Fig.  68. 

and  they  appear  to  take  up  natural  positions  in  the  riffles  better 
than  if  placed  there  by  hand.  This  allows  the  gold  particles  to 
sink  into  the  quicksilver.  The  two  tables  under  the  screen  feed 
to  two  launders,  which  deliver  in  turn  to  the  main  long  sluices 


118         DREDGING   FOR   GOLD   IN   CALIFORNIA. 

on  each  side  and  which,  with  the  tables  under  the  screen,  are 
arranged  with  sections  of  angle-iron  riffles,  most  of  them  placed 
end-ways,  as  shown  in  sketch.  The  save-all  sluice  extends  from 
under  the  screen-launders  to  the  stern  of  the  boat  under  the 
screen-tables.  The  side  sluices  are  now  each  2  ft.  wide  and 
the  save-all  sluice  is  18  in.  wide.  This  method,  however,  is  to 
be  changed  and  simplified  and,  according  to  Mr.  James  Leggett, 
made  much  more  efficient.  The  time  of  clean-up  is  to  be  shortened 
from  one  and  one-half  or  two  hours  to  half  an  hour.  In  the 
new  arrangement,  the  save-all  sluice  extends  from  the  grizzly  to 
a  point  under  the  lower  end  of  the  screen,  where  it  divides  and 
passes  out  on  each  side  of  the  stacker. 

It  is  generally  admitted  that  the  Holmes  system  of  launders 
and  tables  is  the  best  gold-saving  apparatus  in  use  at  the  present 
day  and  it  is  already  employed  by  many  boats.  They  consist  of 
a  wide  table  or  tray  of  iron  plate  directly  under  the  screen  and 
sloping  in  the  same  direction.  This  is  either  fitted  with  riffles 
or  is  a  plain  steel  plate  with  sides.  It  receives  the  screening 
that  empties  from  the  end  onto  another  plate,  sloping  in  the  oppo- 
site direction;  this  in  turn  delivers  into  launders  (Fig.  69),  which 
are  divided,  and  empty  onto  a  set  of  divided  sluices  sloping  toward 
the  stern  of  the  boat  on  either  side  and  fitted  with  riffles  or  other 
gold-saving  apparatus.  The  launders  and  tables  are  generally 
of  steel  with  steel  bottoms,  but  sometimes  they  are  partially  con- 
structed of  wood.  The  following  examples  will  illustrate  the 
practical  application  of  this  form  of  table:  In  Fig.  70  is  shown 
the  arrangement  employed  on  the  Baggette,  the  latest  and  largest 
Risdon  boat,  the  trommel  screen  is  29  ft.  6  in.  long  and  6  ft. 
diam.  The  screening  surface  is  21  ft.  long;  this  length  is 
divided  into  five  sections.  The  holes  in  the  two  upper  divisions 
are  T\  in.  diam.  and  in  the  three  lower  portions  are  ^  in.  Directly 
underneath  the  screen  is  a  plate  8  ft.,  as  long  as  the  screen  and 
fitted  with  angle-rich  cross-riffles.  Two  lower  plates  are  also  ar- 
ranged with  riffles.  They  empty  into  the  launders  as  shown  in 
Fig.  69.  The  launders  are  of  iron  plate,  with  double  bottoms  and 
deliver  to  the  four  sluices  on  each  side,  each  30  in.  wide  and  12  ft. 
long.  The  'save-all'  sluice  is  30  in.  wide  by  28  ft.  long. 

On  the  Butte,  the  arrangement  is  slightly  different.  Two 
shaking  screens  are  employed,  the  upper  one  13  ft.  long  by  4  ft. 


\ 


:  \i 


Fig.  71.     Launder  Delivery  and  Lower  Tables,  with  Angle-Iron  Riffles, 
on  the  Baggette. 


Fig.  72.     Tail  Sluice  on  the  Baggette. 


122 


DREDGING   FOR   GOLD   IN   CALIFORNIA. 


&l/4  in.  wide,  and  the  lower  one  13  ft.  long  by  5  ft.  7  in.  wide  and 
punctured  with  %-in.  holes;  the  undersize  is  carried  onto  a  steel 
tray  divided  lengthwise  by  three  angle-irons  and  sloping  with  the 
screen.  These  irons  prevent  accumulation  of  sand  when  the  boat 


Fig.  73. 

lists.  From  the  lower  end  of  this  tray  the  flow  is  onto  a  riffle-plate, 
B,  the  same  width,  which  in  turn  delivers  into  the  launders,  and 
thence  to  the  sluice-plates. 


THE  METALLURGY  OF  DREDGING. 


123 


The    arrangements    on    El    Oro    are    practically    similar,    with 
some  slight  change  in  the  plan  of  tail-sluice. 

'  A  brief  description  of  the  gold-saving  apparatus  on  the  Fol- 
som  No.  4  will  be  interesting,  as  it  is  the  largest  dredge  in  the 
world.  ^Double  shaking  screens  are  used,  the  upper  one  10  ft.  6 
in.  long  by  11  ft.  11  in.  wide  and  the  lower  one  14  ft.  long  by  12  ft. 
8  in.  wide.  The  save-all  sluice  A,  (Fig.  73)  is  at  such  a  height 
that  it  delivers  onto  plate  B,  under  the  upper  shaking  screen. 
Table  B  delivers  onto  C  and  C  into  the  launders,  which  are  curved 


Fig.  74. 

and  drop  in  steps  toward  the  outside  of  the  boat  corresponding 
to  the  steps  in  the  sluices,  of  which  there  are  seven,  running 
lengthwise  with  the  boat.  Cross-riffles  are  used  and  stops  are 
fitted  at  the  points  shown. 

No.  5  boat  at  Folsom  has  a  most  interesting  arrangement, 
recently  installed.  The  screens  are  not  changed;  the  dimensions 
are:  Upper  screen  16  ft.  long  by  11  ft.  10  in.  wide;  lower  screen 
16  ft.  long  by  8  ft.  9  in.  wide.  They  were  arranged  origin- 
ally as  in  Fig.  74.  The  undersize  from  the  upper  screen  dropped 
onto  table  A  and  that  from  the  lower  onto  table  B.  Table 
A  delivered  onto  plate  C,  and  C  and  B  delivered  into  the  launders, 


124          DREDGING   FOR    GOLD   IN   CALIFORNIA. 

which  were  situated  about  midway  under  the  screens.  Plates  A, 
B,  and  C  were  all  riffled.  The  launders  fed  onto  a  series  of 
Holmes  tables,  as  shown  in  plan.  In  the  new  arrangement,  table 
C  is  removed  altogether.  Table  A  receives  the  undersize  from  the 
upper  screen  and  delivers  to  one  set  of  launders  and  onto  three 
tables,  which  have  been  raised  up.  Plate  B  delivers  the  undersize 
from  the  lower  screen  into  a  set  of  launders  4  ft.  lower  than 
the  first  set  and  these  deliver  in  turn  onto  another  and  lower  set 
of  tables.  Thus  the  product  is  divided  and  the  separate  clean-up 
becomes  useful  in  testing. 

On  another  boat  belonging  to  this  company,  a  grating  (under- 
current) has  been  put  in  the  sluice  and  part  of  the  product  is 
received  on  a  separate  sluice.  Unfortunately  not  enough  of  such 
testing  work  is  done  on  the  dredges  and  the  results  usually  leave 
the  operator  in  the  dark  as  to  his  losses. 

The  gold-saving  efficiency  of  a  dredge  is  affected  by  two 
\J  factors  that  also  influence  stamp-mill  practice.  I  refer  to  the  grade 
of  the  tables  and  sluices,  and  the  amount  of  water  used.  It  is 
considered  that  \l/2  in.  per  foot  is  the  most  efficient  slope 
for  the  tables  and  sluices;  the  amount  of  water  is  variable. 
As  a  matter  of  fact,  no  arbitrary  rule  should  be  blindly  applied. 
The  slope  and  flow  of  water  should  be  adjusted  so  that  all  of  the 
gold  will  come  in  contact  with  the  quicksilver.  Irhpact,  assisted 
x /by  small  'drops'  in  the  sluices  and  a  break  in  the  current  are 
conducive  to  effective  amalgamation.  Too  much  water  at  too 
great  a  speed,  however,  may  carry  off  fine  gold,  some  of  which 
in  the  Oroville  deposits,  is  (to  use  a  well-worn  illustration)  so 
fine  as  not  to  settle  after  two  hours  in  a  bottle  containing  a  weak 
acid  solution.  On  the  other  hand,  if  the  grade  is  so  flat  or  the 
\*  volume  of  water  so  low  as  to  allow  an  accumulation  of  sand  to 
cover  the  mercury,  amalgamation  is  hindered.  The  filling  of  the 
interstices  of  the  cocoa  matting  by  fine  sand  or  slime  is  a  draw- 
back to  that  method  of  gold  saving. 

It  often  happens  that  the  boat  has  a  list  according  to  the 
pull  on  side  lines,  and  the  sluices  on  one  side  may  be  seen  banked 
with  sand,  while  the  riffles  are  covered.  Almost  every  dredge 
has  a  variable  'flotation'  level  at  either  end,  depending  on  the 
hardness  of  the  ground  being  dredged,  and  the  depth  to  which 
the  ladder  is  digging.  Due  to  this  cause  and  the  list,  therefore, 


10 
l^, 

be 


126         DREDGING   FOR   GOLD   IN   CALIFORNIA. 

it  is  seldom  that  the  sluices  and  tables  maintain  the  most  favorable 
angle.  In  any  case,  the  gold  is  so  excessively  fine,  particularly 
at  Oroville,  that  much  of  it  is  lost  even  under  the  most  favorable 
conditions  possible  with  the  present  gold-saving  devices.  The 
extent  of  this  loss  is  not  known,  as  the  small  amount  of  research 
work  has  given  no  results  of  any  value.  This  is  one  of  the  features 
of  dredging  that  surprises  the  millman  and  metallurgist.  Even 
the  technical  mining  engineer  whose  chief  work  lies  among  pla- 
cers— and  this  is  now  recognized  (particularly  in  the  West)  as 
one  of  the  specialties  of  the  profession — has  little  to  offer  in  the 
way  of  authentic  data  regarding  the  actual  contents  of  the  ground 
that  he  may  be  exploiting  and  consequently  he  cannot  know 
his  losses.  No  proper  testing  of  the  tailing  has  been  made; 
automatic  sampling  is  unknown.  Nevertheless,  on  being  ques- 
tioned, the  manager  will  tell  you  that  he  has  sampled  his  tailing  and 
knows  just  what  his  losses  are.  On  closer  interrogation  he  says 
that  he  has  made  his  conclusions  by  careful  pan  and  rocker  work 
at  the  tail-sluice  and  that  what  a  pan  or  rocker  will  not  save,  no 
sluice  or  table  will.  At  assays,  he  sneers. 

Many  mills  built  ten  years  ago  are  now  known  to  have  lost 
large  sums  in  gold  and  silver  that  might  have  been  recoverable ; 
how  many  mines  are  now,  by  improved  appliances  in  the  mill 
proper,  by  fine  grinding,  cyanide,  chlorination,  or  other  chemical 
or  mechanical  means,  reducing  ore  at  a  profit  that  ten  years  ago 
was  pronounced  by  engineers  as  'too  low-grade'  to  pay?  Con- 
sider the  comparatively  recent  improvements  on  the  Rand,  in 
Australia,  and  elsewhere  in  slime-separation  and  the  consequent 
increased  recovery.  In  some  cases  dividends  are  being  paid  en- 
tirely from  this  saving. 

The  dredge  operator  does  not  care  what  the  ground  may 
contain — by  assay — so  long  as  he  is  sure  that  with  the  present 
devices  he  is  saving  all  that  is  commercially  possible.  At  the 
same  time  he  is  open  to  consider  any  improved  methods  of  saving 
you  may  offer  and  says,  in  effect,  that  when  the  process  has 
been  proved  practicable,  he  will  examine  his  ground  (which  will 
no  doubt  then  be  worked  out)  to  see  if  it  contains  the  value  which 
your  method  may  recover !  Not  very  logical,  to  say  the  least 
of  it.  What  would  have  been  the  present  state  of  the  industry  if 


THE  METALLURGY   OF  DREDGING.  127 

this  had  been  the  standpoint  of  miners   since  the  days   of  which 
Pliny  writes? 

There  is  certainly  a  large  loss,  due  to  mechanical  arrange- 
ments, in  the  material  that  passes  over  the  upper  tumbler  and 
into  the  well.  This  is  increased  on  the  Yuba  boats,  where  the 
idler  arrangement  makes  it  difficult  to  take  proper  advantage  of 
the  save-all.  Even  in  boats  without  this  idler,  the  loss  in  the  well 
is  known  to  be  appreciable.  It  is  not  of  much  use  to  attempt  to 
find  an  accurate  method  of  testing  the  gravel  in  place  before 
dredging,  as  the  point  to  be  decided  is  the  absolute  amount  of 
gold  that  is  actually  passing  through  the  dredge  and  being  lost 
at  the  tail  (including  that  which  goes  over  the  stacker),  and  all 
the  gravel  is  not  passed  through  the  dredge. 

Even  the  character  of  this  gold  is  not  known  except  that 
some  of  it  is  excessively  fine.  It  is  possible  that  a  proportion 
of  it  is  not  only  fine,  but  coated  or  otherwise  unfit  for  amal- 
gamation. 'Rusty'  gold,  so-called,  due  to  a  coating  of  silica\ 
and  sesqui-oxide  of  iron  is  not  at  all  amalgamable  and  what  little  V 
of  it  is  caught  is  due  entirely  to  its  specific  gravity.  The  results  J 
of  an  interesting  experiment  conducted  by  Mr.  Charles  Helman, 
partly  in  my  presence,  are  indicative  of  possibilities  in  the  direc- 
tion of  such  research.  In  the  first  place,  however,  it  should  be 
said  that  accurate  automatic  sampling  must  be  applied  over  a 
proper  period  to  get  correct  results.  No  dipping  or  digging  of  a 
haphazard  sample  from  the  tailing-bed  will  do,  nor  is  the  method  of 
placing  a  tub  at  the  end  of  the  sluice  efficient,  for  the  tendency  of  the 
finest  silt  (probably  the  most  valuable  portion)  is  to  flow  off  in 
the  rush  of  water.  In  the  case  mentioned  above,  some  of  the 
muddy  water  collected  carelessly  from  one  or  two  buckets  of  the 
sand  at  a  clean-up  was  filtered  and  the  resultant  impalpable  red- 
dish powder  assayed  $9600  per  ton  in  gold  and  not  only  could  Is 
not  a  'color'  be  detected  with  the  strongest  glass  but  it  was 
also  found  that  none  of  it  would  amalgamate!  This  powder, 
it  is  true,  represented  a  certain  amount  of  concentration,  but 
it  would  stand  a  great  deal  of  dilution,  and  still  carry  values 
that  would  make  even  a  chemical  method  of  treatment  profitable. 
With  dredges  of  the  single-lift  and  long-sluice  pattern  the  re- 
handling  of  this  material  would  be  facilitated.  The  finer  por- 


DREDGING   FOR   GOLD   IN   CALIFORNIA. 

tion  of  the  tailing  might  be  treated  on  the  bank,  if  valuable 
enough. 

An  instance  of  testing  the  tailing  at  the  Conrey  placer 
mines  at  Alder  Gulch,  Montana,  is  of  more  than  passing  interest, 
most  work  of  this  description  having  been  of  a  very  perfunctory 
nature.  Single-lift  dredges  with  long  sluices  supported  on 
a  pontoon  are  used  in  this  district  and  holes  were  drilled  through 
the  tailing  behind  the  dredge  with  a  Keystone  machine.  The 
material  was  found  to  be  unproductive,  with  the  exception  of 
the  bottom  layer  of  6  in.  or  1  ft.,  where  gold  values  were  recovered 
that  made  an  average  of  4  to  6c.  for  the  whole  tailing  mass. 

An  extract  from  one  of  the  earlier  reports  of  the  California 
Bureau  of  Mines  describes  tests  of  muddy  water  from  some  of 
the  best  of  the  Grass  Valley  mills.  In  12  tests,  where  water 
was  taken  from  a  point  nearly  a  mile  below  the  mills,  returns 
were  obtained  by  assay  of  about  $2  per  ton.  It  was  estimated 
that  576,000  gal.  of  this  water  flowed  every  24  hours,  which 
meant  $339  of  float  gold,  to  say  nothing  of  loss  by  imperfect 
pulverization.  A  clean-up  of  the  twentieth  undercurrent  of  the 
Spring  Valley  Hydraulic  Co.,  at  Cherokee,  Butte  County,  Cal. 
yielded  $2600.  This  gold  was  taken  from  material  that  had  been 
sluiced  over  2l/2  miles  of  sluices  and  over  19  other  undercurrents, 
and  even  then  Chinese  were  working  the  tailing  below  this  point ; 
moreover,  the  gold-saving  system  of  this  company  was  supposed  to 
be  the  most  complete  in  the  State,  so  that  it  may  be  easily  seen  how 
loss  occurs  over  the  short-sluice  system  of  a  dredge. 

The  clean-up  is  made  at  intervals  that  vary  on  the  different 
dredges,  as  also  the  time  it  takes  to  accomplish  it.  As  extraction 
ceases  during  the  clean-up,  it  is  important  that  it  should  not 
be  done  oftener  than  is  necessary  to  prevent  loss  by  overloading 
the  tables  and  sluices.  In  some  cases  certain  tables  are  shut  off 
from  the  screen-delivery,  the  flow  being  allowed  to  continue  over 
the  others;  in  this  case  digging  is  not  interrupted.  It  is  doubtful, 
however,  if  this  is  good  practice.  In  other  cases,  the  two  sides 
are  cleaned  up  on  alternate  days,  digging  continuing  all  the  time. 
Usually  a  special  set  of  men  is  kept  for  this  purpose  where 
several  boats  are  in  operation.  On  the  Yuba  until  recently  there 
were  six  boats  operated  by  one  company  and  in  each  case  one 
day  was  devoted  to  the  clean-up.  This  work  is  done  by  three 


130         DREDGING   FOR    GOLD   IN   CALIFORNIA. 

men  who  also  measure  the  bank,  do  surveying  and  other  work, 
and  when  necessary,  call  on  the  boat's  crew  for  assistance.  One 
of  the  party  attends  to  the  melting.  In  this  way  the  men  become 
expert  and  time  is  saved.  The  enforced  idleness  during  clean-up 
time  is  employed  in  making  repairs,  oiling,  etc.  Of  course,  in 
the  case  of  a  company  with  only  one  or  two  boats,  it  would  not 
be  practicable  to  employ  a  special  clean-up  crew. 

To  illustrate  the  most  general  practice  in  cleaning  up,  a 
description  of  the  process  on  Yuba  No.  4  is  given.  A  revolving 
trommel  delivers  onto  eight  tables  on  each  side  and  these  empty 
into  a  stream-down  sluice  (See  Fig.  65).  All  of  the  tables  are 
fitted  with  wooden  riffles  capped  with  a  flat  iron  band.  These 
are  1  in.  square  in  section  and  placed  1*4  in.  apart.  The 
side  tables  are  30  in.  wide  and  13  ft.  long,  and  are  fitted 
with  two  stops  or  permanent  bars,  one  at  centre  and  one 
at  the  lower  end.  The  stream-down  sluice  is  18  in.  wide 
at  the  upper  end,  4  ft.  3  in.  wide  at  the  lower  end  and 
30  ft.  long.  The  clean-up  is  done  on  both  sides  of  the 
boat  at  the  same  time,  by  the  clean-up  force  assisted  by  the 
regular  crew.  The  screen-motor  is  stopped  and,  of  course,  dig- 
ging ceases.  Two  men  loosen  up  the  riffles  on  the  upper  side- 
table  with  a  bar  and  these  are  washed  onto  the  table  with  a 
hose  and  laid  aside.  The  hose  is  then  used — always  pointed 
up-sluice  to  wash  down  the  coarse  gravel — and  each  man  taking 
a  section  above  the  stops,  stirs  the  material  with  a  small  rake, 
something  like  a  currycomb,  so  that  the  coarse  material  passes 
over  the  stop.  The  amalgam,  quicksilver,  and  black  sand  remain 
behind  the  stops;  the  clean-up  men  pass  onto  the  next  table, 
and  so  on,  until  all  of  the  side-tables  are  finished  in  the  same 
manner.  Meanwhile  two  other  men  with  buckets  and  a  wooden 
hand-trowel  scrape  the  material — amalgam,  quicksilver,  and 
black  sand — into  the  buckets,  which  are  then  emptied  into  a 
wooden  tank  that  is  kept  full  of  water.  When  the  tables  have 
been  finished,  the  water  is  removed  from  the  tank  (with  a  basin) 
and  the  material  is  lifted  (with  a  scoop)  and  carefully  fed  into 
the  hopper  of  a  'long  torn'  constructed  as  shown  in  Fig.  77. 
This  sluice  is  14  ft.  long  and  the  width  inside  the  box  is  \2l/2 
inches. 


132         DREDGING   FOR   GOLD   IN   CALIFORNIA. 

Water  is  fed  into  the  hopper  by  a  hose  from  the  pump.  The 
mercury  trap  is  kept  stirred  with  a  long  spike  and  90%  of  the 
amalgam  is  caught  above  the  stop  B  just  above  the  mercury 
trap.  The  amalgam  is  removed  from  the  sluice  and  drained 
in  a  small  inclined  metal  trough  and  the  'quick'  is  collected 
from  the  trap'  in  the  long  torn  and  strained.  The  sand  from 
the  side-tables  is  put  back  into  the  vat  and  passed  through  the 
'torn'  again  with  the  material  collected  from  the  stream-down 
sluice.  The  amalgam  and  mercury  are  thus  collected,  while  the 
sand  remaining  at  the  end  of  the  process  is  replaced  on  the  sluices. 
A  'long  torn'  is  used  on  each  side  of  the  boat  and  the  results 
from  the  side-tables  are  mixed  together  for  retorting  and  melting, 
as  is  the  material  from  the  stream-down  sluices  on  each  side.  The 
trommel  rotates  from  starboard  to  5port,  like  the  hands  of  a  clock 
and  the  material  is  usually  thrown  up  on  the  port  side  of  the  screen, 
but  with  the  side-tables  the  screen-delivery  is  arranged  so  that  most 
of  it  goes  to  the  starboard  tables  and  most  of  the  gold  is  caught 
on  this  side.  The  clean-up  commences  at  7  a.  m.  and  is  completed 
in  from  2  to  3  hr.  Minor  repairs  are  usually  done  at  this 
time  and  the  boat  is  ready  to  continue  digging  about  noon. 
Cleaning  up  was  formerly  done  once  in  every  six  days  but  the 
two  new  boats  (No.  7  and  8)  being  now  completed,  it  will  be  done 
once  in  eight  days. 

The  clean-up  on  the  Leggett  No.  3  is  done  differently.  The 
arrangements  of  the  screen  and  the  sluices  have  been  previously 
explained.  The  riffles  on  the  upper  table  are  first  removed  and 
washed  onto  the  screen,  while  a  full  head  of  water  is  turned  on. 
The  sand  and  mercury  are  carried  down,  the  amalgam  being  re- 
tained behind  a  loose  stop.  The  upper  half  of  the  riffles  on  the 
second  table  are  taken  up  and  washed  and  then  the  lower  portion 
is  treated  in  the  same  way,  one  side  of  the  launder  being  stopped 
previously,  so  that  everything  is  carried  over  one  side-sluice.  The 
lower  sluices  and  the  'save-all'  are  then  cleaned  up.  The  whole 
process  only  takes  about  one  hour  and  with  the  new  system  of 
tables  it  will  take  even  less  time.  The  essential  difference  from 
the  ordinary  method  is  that  the  head  of  water  employed  while 
digging  is  in  use  throughout  the  process.  The  clean-up  takes 
pjace  every  ten  days  and  mercury  is  fed  onto  the  tables  and  sluices 
three  times  between  each  clean-up.  The  only  boats  now  using 


134         DREDGING   FOR   GOLD   IN   CALIFORNIA. 

the  amalgamating  machine  in  cleaning-up  are  the  Butte  and  El  Oro, 
and  the  method  as  practiced  on  these  boats,  though  thorough,  is 
slow. 

The  processes  being  practically  alike,  one  description  will  suffice. 
Each  boat  has  shaking  screens  with  a  table  underneath  with  the 
same  slope  as  the  screens  and  a  second  underneath  the  first,  sloping 
back  toward  the  bow  and  emptying  into  the  launders.  Each  has 
a  triple  divided  sluice-way  sloping  toward  the  stern,  the  tail- 
sluice  on  the  Butte  being  arranged  a  little  differently  from  the 
El  Oro  sluice,  the  riffles  of  the  former  being  continued  a  little 
farther  aft.  The  save-all  sluice  on  the  Butte  discharges  into  the 
well  of  the  boat,  while  the  El  Oro  save-all  sluice  slopes  toward  the 
stern  and  delivers  the  tailing  into  a  pipe  running  through  the  hull. 
The  clean-up,  as  in  all  cases,  commences  at  the  upper  tables  first 
and  follows  down  to  the  tail. 

The  slats  on  each  side  of  the  tables  are  lifted,  by  removing 
the  wedges,  and  the  sections  of  riffles  are  carefully  taken  out  so 
as  not  to  spill  the  'quick'  and  amalgam  that  they  contain.  Then 
the  bottom  of  the  riffle-sections  are  tapped,  scraped,  and  brushed 
into  a  trough,  the  top  sections  being  done  first.  The  material 
from  this  trough  and  the  sand  from  the  tables  (from  which  the 
riffles  have  been  removed)  are  conveyed  by  a  couple  of  Chinamen 
with  pots  holding  about  two  quarts,  to  the  miniature  'long  torn' 
(See  Fig.  78).  In  the  top  of  this,  as  will  be  seen,  is  a  hopper 
with  a  coarse  wire  screen  that  may  be  lifted  out  and  on  which 
the  material  from  the  pots  is  hand-sifted.  A  hose  from  the  pump 
is  turned  into  the  hopper.  Below  is  a  small  set  of  riffles  about 
15  in.  long  and  12  in.  wide,  the  overflow  from  which  goes  into 
a  'Lasswell's  Fine  Gold  Amalgamator'.  This  consists  of  three 
iron  pots  1  ft.  3  in.  diam.  and  1  ft.  8  in.  deep  arranged  at  intervals  of 
\Yz  in.  apart,  the  first  pot  set  on  a  level  higher  than  the  other  two. 
The  three  are  connected  by  syphon  tubes  bent  into  a  short  elbow  at 
the  bottom  to  give  rotary  movement  to  the  water  and  sand,  allowing 
the  heavy  material  to  settle.  The  tops  are  firmly  closed,  an  air-pipe 
being  inserted  in  each.  A  vent  in  the  bottom  is  closed  with  a  nut.  The 
water,  sand,  quicksilver,  and  some  amalgam  passing  over  the  little 
torn  sluice,  go  through  the  series  of  three  pots,  the  mercury  and 
remaining  amalgam  being  deposited  in  the  first.  The  material 
is  carried  into  a  tank,  which  overflows  into  a  launder  discharging 


THE  METALLURGY   OF  DREDGING. 


135 


overboard.  The  'quick'  is  drawn  off  at  the  bottoms  and,  later, 
the  tops  are  taken  off  and  the  amalgam  is  removed.  To  show 
the  efficiency  of  the  process,  the  contents  of  the  vat,  the  result 
from  a  month's  run  of  some  40,000  cu.  yd.,  was  put  through  the 
process  a  second  time  and  only  a  little  over  a  desert-spoonful  of 
quicksilver  was  secured,  and  this  contained  very  little  gold.  The 
material  in  this  vat  is  replaced  near  the  head  of  the  tables  when 
the  riffles  are  again  in  place.  On  the  Butte  the  tail-sluices  are 
fitted  with  one  or  two  sections  of  cocoa  matting,  which  are  rinsed 


Fig.  79.     Jets  for  Shaking  Screen,  on  the  Garden  Ranch  Dredge. 

thoroughly  in  water  and  replaced,  the  material  deposited  in  the 
water  being  treated  with  the  rest  of  the  clean-up  sand.  About 
50%  of  the  amalgam  recovered  is  found  on  the  riffles  in  the  small 
clean-up  sluice  or  on  the  wire  screen  in  the  hopper.  The  contents 
of  each  table  and  the  save-all  sluice  are  taken  separately  and  the 
percentage  separately  calculated.  The  results  show  about  80 
to  85%  of  the  recovery  from  the  upper  table,  12  to  15%  from  the 
lower  sluice-tables,  and  2  to  3%  from  the  'save-all'.  The  last 
product  varies  greatly  in  proportion.  On  these  two  boats  the 
clean-up  takes  place  only  once  per  month.  From  300  to  400  Ib. 
mercury  is  put  on  the  table  and  sluices  after  each  clean-up,  and 


136         DREDGING   FOR   GOLD   IN   CALIFORNIA. 

another  like  quantity  during  the  month.  The  resultant  material 
from  the  clean-up  consists  of  amalgam,  quicksilver,  sand,  and  small 
gravel.  The  cleanest  of  the  amalgam  is  skimmed,  strained  through 
stout  cotton  cloth,  and  the  quicksilver  is  used  again  on  the  tables, 
while  the  amalgam  is  placed  in  a  metal  funnel  with  a  very  small 
hole  at  the  lower  end,  to  drain  off  the  mercury.  The  sandy  portion 
of  the  clean-up  is  panned  first  over  one  tub  to  free  it  from  the 
coarsest  pebbles  and  practically  worthless  material,  and  then  over 
a  second.  The  amalgam  and  quicksilver  are  poured  off  and  treated 
as  before,  the  sand  being  kept  separate. 

There  are  now  two  products  for  the  melting  room:  1.  Amal- 
gam with  a  small  excess  of  mercury;  2.  Black  sand  containing 
lead,  nails,  etc.  In  most  of  the  older  districts,  particularly  those 
that  have  yielded  large  returns  in  the  old  gravel-washing  days, 
the  material  now  being  dredged  contains  a  large  percentage  of 
metal  in  the  form  of  Chinese  and  other  coins,  small  ornaments, 
buttons,  nails,  and  notably  lead  in  the  form  of  shot  and  bullets, 
etc.  Some  of  this  material  is  contained  in  the;  second  product. 
Much,  however,  must  pass  entirely  over  the  tables,  acting  as  a 
sluice-robber;  thus,  nearly  every  dredge  has  its  proportion  of  lead 
bullion  to  be  treated  after  the  clean-up,  every  few  months,  for  this 
material  all  collects  some  amalgam.  With  the  black  sand  too,  are 
collected  traces  of  platinum,  osmium,  iridium,  and  possibly  other 
rare  metals.  These  do  not  amalgamate  in  the  ordinary  way,  and 
it  is  quite  possible  that  a  comparatively  large  amount  passes  over 
the  sluices  and  is  lost. 

But  to  return  to  the  melting  room:  The  amalgam,  forming 
the  first  product,  after  careful  weighing  of  each  portion  separately, 
is  placed  in  an  iron  vessel  and  retorted  in  the  furnace.  The 
crude  gold  from  the  retort  is  in  its  original  'plate'  or  'scale' 
form,  though  still  containing  enough  mercury  to  make  it  adhere  in 
lumps.  It  is  placed  with  a  flux  of  sodium  bicarbonate  and  borax 
in  a  graphite  crucible  (previously  carefully  annealed)  and  smelted 
in  the  usual  manner.  It  is  then  poured  into  the  iron  mold,  coated 
inside  with  the  smoke  of  burning  rosin  to  give  the  bar  a  good 
surface. 

The  mercury  from  the  dredge  is  cleaned  at  intervals,  par- 
ticularly when  the  boat  is  idle,  by  retorting,  and  leaves  a  white 
dross-like  looking  residue,  which  carries  $16  per  ounce  in  gold ; 


THE    METALLURGY    OF    DREDGING.  137 

this  is  very  brittle,  possibly  by  reason  of  the  presence  of  antimony. 
In  a  recent  retorting  of  963  Ib.  of  mercury,  55.5  oz.  of  this  alloy 
was  produced.  It  is  sometimes  melted  with  the  bar  and  imparts 
a  whitish  color  to  the  gold.  The  second  product  is  screened,  to 
separate  the  shot  and  nails,  etc.  and  to  eliminate  the  magnetic 
sand,  the  former  material  being  placed  in  a  clean-up  barrel  with 
water  and  iron  rollers,  and  rotated.  After  this  cleaning,  the  nails 
and  iron  are  removed  with  a  magnet  and  thrown  away,  while  the 
residue,  including  the  lead,  is  retorted  to  drive  off  the  mercury. 
The  lead  matter  that  is  produced  is  then  smelted  with  flux  arid 
the  resultant  base  bullion  is  worth  $1.25  to  $1.50  per  oz.  This 
is  shipped  to  the  Selby  smelter  with  the  gold.  The  black  sand 
that  is  saved  varies  in  value ;  that  from  the  El  Oro  and  the  Butte 
for  some  six  months  averaged  $140  per  ton.  Great  quantities, 
of  course,  go  over  the  tables ;  no  special  effort,  in  fact  being  made 
to  save  it.  At  Folsom  the  system  is  similar  to  that  described  on 
the  Yuba  No.  .4.  A  vat  and  torn  sluice  are  used  and  the  sandy 
material  from  the  torn  is  put  through  the  vat  a  second  time. 

With  regard  to  the  value  of  the  ground  in  the  different  dis- 
tricts, this  varies  greatly  in  the  same  locality,  and  most  of  the 
drilling  tests  disclose  the  fact  that  the  highest  returns  are  obtained 
from  channels  and  patches  (probably  old  river  bars),  but  in 
dredging  a  tract  the  results  of  the  drilling  must  be  averaged  to 
obtain  the  value  of  the  whole  area,  which  is,  as  a  rule,  all  moved. 
For  instance,  if  a  rectangular  area  of  100  acres  is  intersected  by 
two  or  three  irregular  and  winding  channels  with  'islands'  be- 
tween and  the  values  are,  on  the  average,  25c.  per  yd.  in  the  chan- 
nels and  8c.  per  yd.  elsewhere  over  the  tract,  and  the  cost  of  dredg- 
ing is  6c.  per  yd.,  then,  though  to  dredge  only  the  low-grade 
ground  outside  the  channels  would  probably  not  yield  a  profitable 
rate  of  interest,  it  might  be  found  advisable  to  dredge  the  whole 
tract  systematically  rather  than  follow  the  irregular  channels  and 
rich  patches  even,  if  when  lumped  together  they  formed  a  fairly 
large  proportion  of  the  whole  area.  Such  questions  as  these, 
however,  occur  constantly  to  the  dredging  engineer  and  must  be 
treated  separately  and  weighed  strictly  from  a  business  point  of 
view.  The  vital  and  only  question  to  be  decided  is,  whether  at 
the  completion  of  dredging  a  tract  of  auriferous  alluvial  land,  the 
operator  will  have  made  the  maximum  amount  of  profit  possible, 


138         DREDGING   FOR   GOLD   IN   CALIFORNIA. 

giving  the  important  factors  of  time  and  interest  due  consideration. 
As  regards  the  prospect  values  of  dredging  ground  and  the  re- 
covery percentages  therefrom,  in  these  three  districts,  reference  to 
the  chapter  on  'Prospecting'  will  provide  actual  cases. 


VI.     COSTS. 

No  general  table  of  the  cost  of  a  completed  dredge  can  be 
given  on  the  basis  of  capacity,  as  so  much  is  governed  by  other 
conditions  such  as  special  design,  locality,  repair  facilities,  builders, 
etc.  The  actual  cost  of  a  complete  dredge  today  ranges  from 
$40,000  to  $150,000.  Even  the  range  in  price  of  boats  of  the 
same  nominal  bucket-capacity  varies  greatly. 

The  three  prime  factors  to  be  kept  in  mind  are: 

1.  To  obtain  the  greatest  possible  output  in  a  given  time. 

2.  To  maintain  the  highest  percentage  of  working  time. 

3.  To  secure  the  highest  possible  extraction. 


Fig.  80.     7^-Cubic  Feet  Bucket  on  Boston  No.  4.     Front  View. 

Boats  of  3  cu.  ft.  bucket-capacity  dig  on  an  average 
of  40,000  cu.  yd.  per  month,  and  those  of  larger  capacity  range 
over  200,000  cu.  yd.  per  month,  as  in  the  case  of  the  No.  4  boat 
of  the  Folsom  Development  Co.,  which  is  fitted  with  buckets  of 
13  cu.  ft.  capacity.  This  is  the  largest  dredge  in  the  world.  The 


140 


DREDGING   FOR   GOLD   IN   CALIFORNIA. 


fixed  costs  of  dredging  form  a  large  percentage  of  the  total 
operating  cost,  and  do  not  vary  as  much  as  might  be  expected 
with  the  capacity  of  the  machine.  Therefore,  it  will  be  obvious 
how  advantageous  it  is  to  obtain  a  large  relative  output;  in  fact, 
production  is  limited  mainly  by  the  mechanical  difficulties,  and 


Fig.  81.     Same  as  Fig.  80,  but  Rear  View. 

the  increasing  percentage  of  gold  lost  in  boats  digging  more  than 
a  certain  yardage.  It  has  been  authoritatively  stated  that  with  the 
present  type  of  dredge  it  is  impossible  to  design  a  screening  and 
disintegrating  arrangement  capable  of  properly  treating  and  pre- 
paring for  the  gold-saving  tables  over  a  certain  fixed  quantity  per 
day,  irrespective  of  the  digging  capacity  of  the  boat,  and  that  after 


COSTS.  141 

this  ratio  between  digging  and  screening  capacity  has  been  ex- 
ceeded, there  is  an  increasing  loss  in  gold  per  yard  dredged.  To 
take  an  arbitrary  case  for  illustration,  let  us  suppose  that  in  a  boat 
of  the  most  modern  design,  handling  100,000  cu.  yd.  per  month, 
the  maximum  gold-saving  efficiency  has  been  reached ;  then,  if 
the  digging  capacity  be  increased  to,  say,  150,000  cu.  yd.  per  month, 
the  percentage  of  gold  saved  per  yard  will  be  decreased,  though 
not  necessarily  in  the  same  ratio  as  the  increase  in  digging  capacity. 
On  this  last  point  hinges  the  practice  on  the  larger  boats  at  Folsom. 
Though  it  is  admitted  that  a  certain  amount  of  gold  is  lost  by 
increasing  the  output,  it  is  contended  that  more  net  profit  is  made. 
Another  arbitrary  example  will  again  illustrate:  A  dredge  is 
operating  100  acres  of  gravel  property  30  ft.  deep  and  containing 
20c.j)er  yd.  (prospect  value)  of  which  15c.  per  yd.  is  saved  at  a 
total  operating  cost  of  7c.  per  yd.,  when  digging  100,000  yd.  per 
month.  The  monthly  operating  cost  would  then  be  $7,000.  The 
capacity  may  be  increased  to  200,000  cu.  yd.  per  month,  with  an 
equivalent  loss  of,  say,  2c.  per  yd.  (probably  high)  and  a  decreased 
working  cost  of  3c.  per  yd.  To  sum  up  results :  In  the  first 
case  the  dredging  of  the  100  acres,  or  4,840,000  cu.  yd.  is  completed 

in  4,840.ooo  =  48.40  months  which  is  4  years  and   12  days,   and  the 

100,000 
gross  extraction  is  4.84Q.oooxi5  _  $726,000  at  a  cost  of  4.840.ooox7     $333, 

ipo  100 

800,   leaving  a  net  profit   of  $393,000.       In   the   second   instance, 

where  the  capacity  of  the  dredge  is  doubled,  the  work  has  con- 
sumed two  years  and  six  days  and  1840.000x13  =  $629,200  has  been 

*  J  100 

extracted  at  a  cost  of  4.840.000x4     $193600,  which  leaves  a  net  profit 

100 

of  $435,600;  a  gross  saving  over  the  former  method  of  $42,600 
in  cash  and  over  two  years  in  time, which,  if  the  cost  of  the  dredge 
was,  say,  $250,000  would  mean  an  added  saving  in  interest  of 
about  $15,000  per  year  on  the  investment  or  $30,000  for  the  two 
years,  that  is,  a  total  profit  of  about  $72,600  over  the  first  case. 

The  second  factor  that  adds  to  the  cost  is  loss  of  digging  time, 
as  the  fixed  charges  go  on  and  no  gold  is  being  produced  to 
counterbalance  them,  and,  of  course,  there  is  the  loss  in  profit  and 
interest.  The  design  and  construction  of  the  parts,  the  character 
of  the  ground  being  dug,  and  proper  facilities  for  repair,  are  the 
chief  elements  governing  this  loss,  though  certain  necessary 
operating  conditions  and  the  clean-up  also  account  for  lost  time. 


142         DREDGING   FOR   GOLD   IN   CALIFORNIA. 

These  last  items,  are  said  to  be  hard  to  obviate,  though  in  one 
case  mentioned  later,  it  is  expected  that  the  time  of  clean-up  will 
be  reduced  from  the  usual  period  of  from  two  hours  or  half  a  day 
down  to  as  little  as  half  an  hour !  The  following  examples  from 
Oroville  will  give  an  idea  of  how  time  is  lost. 

1.  Lost  time  on  the  Butte  for  32  months  was  18.5%  of  pos- 
sible dredging,  time  made  up  as  follows : 

Percentage 
Cause  of  time  lost. 

Stepping    ahead     9.10 

Ladder  and  bucket-line    21.36 

Stacker     6.70 

Winches 2.25 

Screen 4.40 

Water-pump    1.10 

Sand-pump   3.81 

Lines  2.57 

Power 15.70 

Other  causes  (high  water  and  holidays) 27.41 

Clean-up     5.60 

The  sand-pump  ran  12.3%  of  the  time. 

2.  Lost  time  on  El  Oro  for  20  months  was  33.41%   of  pos- 
sible dredging  time;  the  sand-pump  ran  for  12.15%. 

Percentage 
Cause  of  time  lost. 

Stepping  ahead 6.29 

Ladder  and  bucket-line  44.34 

Stacker  5.34 

Winches 2.34 

Screen 12.22 

Water-pump    3.90 

Sand-pump 1.29 

Lines   2.54 

Power  3.33 

Other  causes  15.38 

Clean-up 3.30 

For  the  calendar  years  1903  and  1904  the  lost  time  on  the 
Exploration  No.  I  was  30.6%  and  32.8%  respectively  of  the  pos- 
sible time.  The  details  are  most  interesting  and  are  as  follows : 

The  best  work  done  by  the  Lava  Beds  No.  3  boat  was  during 
the  19th  month  of  operation  when  an  average  working  time  of 
22  hr.  per  day  was  attained.  The  2  hr.  per  day  of  lost  time 


COSTS. 


143 


included  all  stoppage  of  any  kind;  of  course,  this  is  a  record  and 
no  such  average  is  kept  up.  On  some  of  the  Folsom  boats,  how- 
ever, it  is  claimed  that  the  average  working  time  over  a  long 
period  amounts  to  over  20  hours  per  day. 

From  the  following  tables,  which  refer  to  six  boats  of  the 
Feather  River  Exploration  Consolidated,  the  lost  time  may  be 
calculated : 

Table   of   Lost   Time    on    Exploration    No.    1. 
For   Year    Ending  January   1,    1904. 


0 

s 

o 

be 
C 

•««s 

•S-3 

«3 

u. 

S 

c 

in 

• 

a 

I 

3 

J 

ix 

T3 

£*.* 

£1 

a 

ti 

OJ 

OB 

Month 

II* 

a  3 

1* 

35 

(N 

i* 

1* 

a> 

0 

IM 
O 
£ 

O 

I* 

3 

£ 

"o 

Average 
dredged  ] 
of  runnir 

J|S 

January  .  . 

7.1 

15.6 

5.8 

1.0 

3.1 

5.1 

21.6 

8.4 

32.3 

22.3 

77.7 

1,257 

1,000 

February.. 

7.8 

0.0 

5.0 

2.2 

9.1 

6.5 

13.2 

0.0 

56.2 

46.4 

53.6 

2,007 

1,076 

March    ... 

18.4 

1.6 

1.6 

17.6 

ZS.3 

14.4 

4.9 

1.7 

16.4 

34.9 

65.1 

1,514 

986 

April  

58.4 

7.8 

0.7 

2.0 

0.0 

8.0 

12.7 

2.7 

7.7 

21.9 

78.1 

2,100 

1.637 

May  

76.5 

1.0 

0.0 

0.5 

1.5 

4.1 

3.0 

6.8 

6.6 

39.0 

61.0 

1.900 

1,160 

June 

73  9 

4  4 

1  0 

6  2 

0  0 

0  7 

2  6 

7  1 

4  2 

39  9 

60.1 

1,890 

1,135 

July  

23.4 

5.0 

6^2 

6.2 

1.0 

33.0 

3.0 

6.5 

15.7 

37.0 

63.0 

2,114 

1,332 

August  .  .  . 

21.1 

9.4 

24.3 

9.0 

2.3 

4.4 

12.8 

11.7 

5.0 

24.2 

75.8 

1.958 

1,484 

September. 

20.4 

19.7 

13.6 

1.1 

1.0 

7.7 

11.0 

14.6 

10.9 

24.0 

76.0 

2,053 

1,560 

October  

22.3 

9.1 

9.0 

2.0 

13.7 

7.0 

9.0 

16.3 

11.6 

23.0 

77.0 

2.135 

1.644 

November  . 

19.4 

18.1 

10.0 

4.2 

2.3 

1.5 

12.8 

11.5 

20.2 

24.3 

75.7 

1.752 

1,314 

December.. 

20.4 

19.0 

1.7 

1.8 

7.8 

2.2 

12.4 

5.2 

29.6 

30.7 

69.9 

2.017 

1.412 

Totals   and 

Averages  .  . 

30.7 

9.4 

6.6 

4.5 

5.4 

7.9 

9.9 

7.7 

17.9 

30.6 

69.4 

1,875 

1,300 

Table   of   Lost  Time   on   Exploration   No.    1. 
For  Year   Ending  January   1,    1905. 


2 

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c 

0) 

to 

0) 

J2 

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in 

a 

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0) 

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c. 

Causes 

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T3  cfl  c 

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ss^ 

*o  >> 

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CJ  ^o 

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3 

u 

— 

13 

0) 

(u'O  £ 

OQ 

0 

I 

as 

<I"O*S 

21 

Jan.     . 

23.9 

12.3 

9.1 

1.6 

25.6 

4.8 

0.4 

6.5 

2.6 

13.2 

59.2 

40.8 

1.365 

657 

Feb.   ... 

6.8 

6.8 

9.9 

4.2 

14.9 

9.4 

23.3 

8.2 

3.2 

13.3 

42.8 

57.2 

1.928 

1,103 

Mar.   ... 

7.9 

33.7 

5.9 

8.1 

3.1 

17.5 

9.9 

5.4 

8.5 

32.5 

67.5 

l.%7 

1.328 

April  ... 

6.8 

13.2 

6.3 

5.6 

0.9 

10.5 

14.3 

5.8 

36.6 

24.1 

75.9 

2,229 

1.692 

May    ... 

1.8 

21.0 

12.9 

8.9 

12.7 

0.7 

1.5 

11.8 

3.8 

24.9 

22.9 

77.1 

1,9% 

1.539 

June   ... 

0.9 

20.6 

21.5 

1.9 

1.4 

0.3 

14.0 

14.3 

5.0 

20.1 

24.8 

75.2 

1,806 

1,358 

July    ... 

2.5 

12.3 

26.2 

2.1 

6.9 

0.6 

2.6 

12.3 

4.9 

29.6 

24.0 

76.0 

1.883 

1,431 

Aug.  ... 

0.7 

20.1 

12.7 

0.1 

41.4 

5.0 

9.1 

3.6 

2.5 

4.8 

44.3 

55.7 

2,277 

1,268 

Sept.  ... 

12.4 

30.4 

6.0 

1.7 

0.6 

2.5 

9.1 

6.9 

2.8 

27.6 

28.6 

71.4 

1.942 

1,387 

Oct.    ... 

37.2 

12.2 

10.2 

1.9 

0.3 

6.8 

0.6 

7.8 

1.5 

21.5 

25.5 

74.5 

2,098 

1,563 

Nov.   ... 

25.6 

48.9 

2.5 

0.8 

0.3 

0.3 

4.2 

6.6 

1.2 

9.6 

34.5 

65.5 

2,050 

1.343 

Dec.   ... 

1.8 

14.4 

5.3 

11.2 

6.2 

0.1 

1.4 

6.4 

2.8 

50.4 

30.9 

69.1 

2.166 

1,497 

Totals  and 

Averages  .  . 

10.7 

20.5 

10.7 

3.5 

9.9 

2.6 

7.9 

9.0 

3.5 

21.7 

32.8 

67.2 

2,005 

1.347 

144 


DREDGING   FOR   GOLD   IN   CALIFORNIA. 


Dredge 

No. 

1 

2 
3 
4 

5 
6 


January,  1906. 

Period. 
16  days  ending  January  31 ... 


Actual 
dredging 

time 
Hours. 

..312 
...267 
...237 
...178 
...211 

..512 


Actual 

February.  1906.        dredging 

time 

Month  ending.  Hours. 

February  28 550 

" 542 

" 596 

11 554 

".., 510 

..566 


Total 1,717 


3,318 


March.  1906. 


April.  1906. 


May.  1906. 


Actual 
dredging 

time 
Hours. 

517:00 
605  :40 
589 :35 
685:30 
562 :05 
613:40 


Total..  3,573:30 


Dredge         Month 
No.            ending. 

1 

March  31  .  . 

2 

"        ".:.-.. 

3 

"        "  .  . 

4 

" 

5 

a             tt 

6 

tt             a 

Month 
ending. 

April  30.. 


Actual 
dredging 

time 
Hours. 

.  598:10 

.  629:25 

.  655:05 

.  310:05 

.  590:20 

.  582:50 

3,365  :55 


Month 
ending. 

May  31 . . 


Actual 

dredging 

time 

Hours. 

.  559:45 
490:05 
672 :25 
659 :20 
561:00 
634.40 

3,577:15 


The  following  cases  of  lost  time  for  two  of  the  boats  belong- 
ing to  the  Yuba  Consolidated  Gold  Fields  are  interesting  in  com- 
parision : 


1.     Lost  time  on  Yuba  dredge  No.  i  for  the  12  months  ending 
January  1,   1906,  was  32.8%   of  possible  dredging,  time  made  up 


as  follows : 


Cause 


Percentage 
of  time  lost. 


Stepping  ahead 5.4 

Ladder  and  bucket  line  32.7 

Spuds    2.1 

Conveyor    6.6 

Hopper  2.1 

Screen    7.4 

Water-pipes  and  pumps   8.3 

Service  cables 2.9 

Power  4.7 

Electrical   repairs    1.7 

Oiling    2.9 

Clean-up  8.5 

Miscellaneous  repairs   (inc.  holidays) 14.7 


COSTS.  55^         145 


2.  Lost  time  on  Yuba  dredge  No.  2  for  the  12  months  ending 
January  1,  1906,  was  30.4%  of  possible  dredging,  time  made  up 
as  follows: 

Percentage 
Cause  of  time  lost. 

Stepping  ahead    6.1 

Ladder  and  bucket-  line  18.8 

Spuds    3.2 

Conveyor    24.5 

Hopper   2.1 

Screen 4.5 

Water-pipes  and  pumps 2.1 

Service  cables    4.0 

Power  6.4 

Electrical  repairs  1.0 

Oiling 3.8 

Clean-up  12.2 

Winches   , 1.8 

Miscellaneous  repairs  (inc.   holidays) 9.5 

The  bucket-line  in  every  instance,  as  will  be  observed  by  an 
analysis  of  the  above  authentic  cases,  is  the  chief  time-loser  and 
is  the  part  most  often  requiring  repair.  The  buckets  vary  in 
shape,  but  the  material  and  strength  (other  than  that  due  to  de- 
sign) are  much  the  same  in  every  case.  The  wear  on  the  lips, 
bottoms,  and  pins  (the  chief  wearing  parts  of  the  bucket),  varies  so 
much  with  the  nature  of  the  ground,  etc.,  that  citation  of  par- 
ticular cases  would  not  be  of  much  use. 

The  lips,  as  has  been  stated,  are  either  of  manganese  steel  or 
nickel  steel.  The  hoods  on  the  older  boats  are  of  forged-sheet 
steel  and  often  in  three  sections,  riveted  together,  but  practically 
all  hoods,  except  possibly  those  of  the  Risdon-type  buckets,  are 
now  made  of  cast  steel  and  thicker  than  formerly.  On  El  Oro, 
the  first  lot  of  buckets  supplied,  although  they  had  cast-steel  hoods 
and  manganese  steel  lips,  were  not  of  proper  design  nor  was  the 
material  of  good  quality,  and  they  only  lasted  six  months.  The 
next  lot  were  of  similar  material,  but  evidently  of  better  quality, 
as  they  lasted  18  months  in  the  same  character  of  ground.  It 
was  found  that  as  the  lips  wore  out  from  the  cutting  edge  back 
to  the  lower  end,  the  angle  was  altered  and  the  cutting  power 
impaired,  so  that  on  the  next  lot  of  buckets  the  lip  was  flared  out 
at  the  top  and  after  wearing  they  had  about  the  original  angle 
in  the  first  case.  The  lip  was  originally  9  in.  long  and  1%  in.  thick. 


146 


DREDGING   FOR   GOLD   IN   CALIFORNIA. 


but  now  is  9  in.  long  and  the  upper  half  is  2  in.  thick,  while  the  por- 
tion that  is  riveted  onto  the  hood  is  only  1  in.  thick.  The  present 
hoods  are  24  in.  thick. 

In  some  soft  ground  near  the  south  end  of  the  Oroville  district 
the  hoods  and  lips  in  a  Bucyrus  bucket-line  lasted  two  and  one- 


Fig.  82.     Upper  Tumbler  of  El  Oro  No.  1,  stripped  of  Wearing  Plates. 

half  years,  while  an  exact  counterpart  of  the  above  line  on  the 
Lava  Beds  No.  2,  digging  in  hard  ground,  was  sent  to  the  scrap 
heap  in  nine  months. 

A  Bucyrus  dredge  at  Oroville  found  it  necessary,  through 
wear,  to  replace  all  the  buckets  in  an  average  of  12  months. 
Another  boat  in  the  same  district,  with  precisely  the  same  buckets, 
has  been  running  already  over  a  year  and  the  buckets  are  estimated 


COSTS.  147 

to  be  good  for  another  year  at  least.  The  difference  in  this  case 
is  due  entirely  to  the  nature  of  the  ground  to  be  dredged.  In  the 
first  case  the  ground  was  hard  gravel  strongly  cemented  together, 
and  in  the  second,  the  material  was  chiefly  sand  which  'ran'  or 
caved  to  the  buckets,  making  the  work  chiefly  a  lifting  proposition. 


Fig.  83.     Lower  Tumbler  of  El  Oro  No.  1,  showing  Wearing  of  Cushion  Plates. 

It  was  thought  by  the  designers  of  one  boat  that  if  the  lip 
was  made  higher  in  the  centre,  it  would  last  longer,  the  greatest 
wear  being  thought  to  be  at  that  point,  but  in  practice  it  did  not 
seem  to  be  of  much  benefit.  The  usual  manganese  steel  in  the 
lips  is  made  under  the  Hadfield  patent,  but  the  Bucyrus  Co.  is 
now  supplying  a  manganese  steel  lip  as  well.  The  Marion  Steam 
Shovel  Co.  is  also  supplying  a  lip  of  what  is  termed  'hard  tough' 
steel,  which  they  guarantee  to  last  as  long  as  the  other.  This  is 


148 


DREDGING   FOR    GOLD   IN   CALIFORNIA. 


now  being  tried  on  some  of  the  new  Yuba  boats  on  the  same  line 
with  bucket  lips  of  the  Hadfield  steel.  Fig.  83  shows  buckets 
with  Hadfield  manganese  steel  that  have  been  digging  for  22 
months,  and  are  still  in  use  on  the  Yuba  No.  2. 

On  the  Ashburton   at   Folsom  the   bucket  lips   are   of   nickel 
steel,  8  in.  long  by  1^4  in.  thick,  and  forged  at  the  company's  shops. 


Fig.  84.     Bucket  Line  of  the  Ashburton  Dredge.     Lips  of  Nickel  Steel. 

On  the  latest  and  largest  Risdon  boat,  the  Baggette,  just 
completed  at  Oroville,  the  bucket  lips  are  of  both  nickel-tool  steel 
and  manganese  steel,  and  are  2  in.  thick  on  the  digging  face,  1  in. 
at  the  back  and  11  in.  deep;  the  hoods  and  bottoms  are  of  flange 
steel,  the  former  ^g  in.  thick,  and  the  pins  and  bushings  are  of 
manganese  steel.  The  Risdon  bucket  still  retains  its  deep  and 
somewhat  narrow  shape,  while  the  modern  tendency  seems  to 
make  for  wide  and  shallow  buckets  of  large  capacity  that  will 
dump  cleanly  over  the  upper  tumbler. 

Pins  are  a  source  of  expense,  and  have  undergone  many 
modifications  and  changes.  In  one  of  the  Lava  Beds  Co.'s  boats 
pins  of  so-called  projectile  steel,  made  by  the  Risdon  Company, 


150 


DREDGING   FOR    GOLD   IN   CALIFORNIA. 


lasted  for  twelve  months  in  hard  cemented  gravel,  while  Fig.  85 
shows  a  pin  and  bucket-bottom  from  the  Yuba  No.  I,  which  were  dis- 
carded after  eighteen  months  constant  service.  In  this  case  the 
dotted  lines  show  the  original  outline  of  pin  and  bottom  at  wearing 
parts ;  the  eye  of  the  bucket-bottom,  as  may  be  noticed,  is  worn 
down  to  almost  the  thinness  of  a  knife-edge. 


Fig.  86.     Showing  Wear  of  Bucket  Bottom  and  Pin  after  18  Months  Service 
on  Yuba  No.  1.     Dotted  Lines  show  Original  Outline. 

Instructive  records  have  been  kept  •  of  the  li-fe  of  various 
pins  on  the  Butte  at  Oroville,  as  follows : 

Material  Wear  Months 

(Original  pins)    Soft  machined  steel 6  (extreme). 

Rolled  steel  with  welded  heads (Said  to  be  very  poor.) 

Marine  steel  from  the  Boston  Machine  Shops 12  to  14. 

Marine  steel  from  San  Francisco 6  to  8. 

El   Oro   shops,  tool   steel 5. 

Cambria   Steel   Works 10. 

At  another  locality,  common  shafting  was  found  to  wear 
from  four  to  six  months,  and  Harveyized  armor-plate  lasted  twelve 
months  and  over,  but  could  only  be  machined  with  difficulty,  as 
it  was  too  hard.  The  pins  on  the  Lava  Beds  boats  are  now  made 


COSTS.  151 

in  three  different  sizes,  3%,  4*4,  and  4^  in.  diam.,  and  are  made 
of  so-called  marine  steel  at  the  Boston  Shops,  the  larger  sizes 
being  used  as  the  bushings  wear.  On  the  Exploration  No.  2,  also 
a  5-cu.  ft.  bucket  boat,  the  pins  of  the  same  material  and  make, 
are  3|§  in.  diam.  The  manganese  steel  pins  on  the  Baggette  are 
3  in.  thick,  and  solid.  On  the  Exploration  No.  /,  a  Risdon  boat, 
which  has  changed  its  bucket-line  for  a  Bucyrus  close-connected 
line,  the  pins  are  2{j-J-  in.  diam.,  and  are  of  machine-steel.  A 
forged-steel  pin  of  3%  in.  diam.  was  used  on  El  Oro ;  and  on  this 


Fig.  87.     Bucket  Line,  showing  Wear  of  Lips  after  22  Months 
Continuous  Service. 

and  several  other  boats  a  solid  manganese  pin  of  about  the  same 
diameter  has  been  replaced  by  a  hollow  manganese  steel  pin  of 
4l/2  in.  diam.,  with  a  hole  of  l^J  in.  through  it.  This  last  pin  has 
been  in  use  for  a  year  with  the  5-cu.  ft.  buckets  on  El  Oro,  and 
seems  to  give  perfect  satisfaction.  Some  Harveyized  pins  on  the 
same  boat  have  been  on  for  a  year  and  a  half,  and  are  still  in  use. 
At  Folsom  the  pins  do  not  differ  materially  in  size  or  material 
from  boats  of  equal  capacity,  while  on  the  No.  4  boat  of  the  Fol- 
som Development  Co.  the  pins  are  of  3%  nickel-steel. 

At  one  of  the  old  Risdon-type  boats  at  Oroville,  I  observed 
an  interesting  operation :  The  bucket  line  (3  cu.  ft.  capacity)  was 
lying  on  the  bank,  and  my  attention  was  drawn  to  the  scene  by 
a  number  of  small  explosions.  On  arriving  at  the  spot  I  found 


152          DREDGING   FOR    GOLD   IN   CALIFORNIA. 

that  nearly  all  the  pins  in  the  line,  which  were  only  slightly  over 
two  inches  in  diameter,  were  broken,  and  the  method  of  abstract- 
ing the  ends  was  unique.  Two  pieces  of  flat-iron  bar  were 
driven  in  at  the  link  between  the  broken  ends  of  the  pin,  and  a 
small  charge  of  dynamite  being  exploded  between  the  bars,  the 
force  drove  the  pins  partly  out  at  the  ends  of  the  eye.  In  this 
same  bucket-line  a  majority  of  the  lips  were  cracked — in  some 
cases  at  several  points  and  directly  across,  only  being  held  to- 
gether by  the  rivets  through  the  hood. 

Pins  vary  considerably,  in  first  cost,  according  to  their  com- 
position. The  hollow  4^>  manganese  steel  pins  on  El  Oro  cost 
$25  each ;  the  Harveyized  steel  cost  $45,  and  the  ordinary  high 
carbon  forged  steel  cost  $16,  so  that  the  price  must  be  considered 
as  well  as  the  life. 

The  bushings  used  are  made  semicircular  because  the  wear 
is  practically  all  on  the  rear  end  of  the  eye.  They  are  shown  in 
Fig.  86,  and  are  almost  universally  of  manganese  steel  and 
about  y%  in.  thick.  An  interesting  innovation  in  the  method  of 
making  these  was  shown  to  me  by  Mr.  Krug  in  designing  a  new 
bucket-bottom,  the  object  of  which  was  to  obviate  change  in 
pitch*  distance  and  thereby  lengthen  the  wear  of  the  line.  The 
bushing  is  made  slightly  thinner  at  the  centre,  and  thus  on  wear- 
ing at  the  edges  to  the  same  thickness,  an  ordinary  bushing  may 
be  put  in. 

Solid  cast  iron  or  steel  is  used  by  some  dredgemen  for  lad- 
der-rollers, and  others  use  a  special  quality  called  'semi-steel' ; 
they  may  also  be  made  hollow.  On  El  Oro  the  first  lot  of  rollers 
were  of  ordinary  cast  iron,  and  lasted  one  year.  Rollers  of 
'semi-steel'  were  then  put  on  and  have  already  lasted  fifteen  months, 
and  appear  to  be  hardly  worn  at  all.  They  are  placed  7  ft. 
apart.  Solid  rollers  are  sometimes  as  small  as  eight  inches  in 
diameter,  while  hollow  rollers  run  up  to  14  in.  The  best  results, 
however,  appear  to  be  given  with  manganese  steel  rollers,  which 
preserve  their  surface  and  do  not  wear  the  bucket-bottoms  un- 
duly. At  times  the  rollers  stick,  and  it  is  remarkable  in  such  a 
case  how  quickly  they  will  wear  down  flat. 

It  is  difficult  to  obtain  the  correct  relation  between  the  ma- 


*The  'pitch'  of  a  bucket-line  is  the  distance  between  the  centre  or  one  rear  'eye' 
and  that  of  the  rear  'eye'  in  the  bucket-bottom  immediately  behind  it  when  coupled. 
The  constant  wear  on  the  pins  and  bushings  changes  this  distance,  and  allows  more 
'play'  and  consequently  more  wear  in  the  whole  line. 


COSTS. 


153 


Fig. 


Wear  Plates  for  Lower  Tumbler. 


terial  used  in  the  bucket-bottoms  and  that  in  the  wearing-plates 
and  shoes  on  the  tumblers.  At  present  the  former  is  generally 
made  of  high  carbon  steel,  and  the  latter  of  manganese  steel  or 
nickel-steel,  and  one  bucket-line  will  wear  out  several  sets  of 
'cushion'  or  wearing-plates  on  the  tumbler.  On  the  Yuba  boats 


Fig.  89.     Wear  Plates  with  Lugs  for  Upper  Tumbler. 


154         DREDGING   FOR    GOLD   IN   CALIFORNIA. 

nickel-steel  shoes  and  plates  are  used  on  the  upper  tumblers,  and 
last  for  six  months,  while  the  lower  tumbler  wearing-plates  are 
of  manganese  steel,  and  though  they  last  over  a  year  the  ten- 
dency is  to  break  rather  than  wear.  It  might  be  at  first  sup- 
posed that  the  proper  relation  would  be  to  have  wearing-plates 
last  the  same  period  as  the  bucket-bottoms,  but  this  is  not  so. 
A  set  of  wearing-plates  will  cost,  say,  from  $600  to  $700,  and  a 
bucket-line  between  $10,000  and  $30,000,  so  that  the  object  is 
thus  at  all  hazards  to  lengthen  the  life  pf  the  bucket-line.  It  is 
not  a  difficult  job  to  replace  wearing-plates,  and  does  not  occa- 
sion an  undue  loss  of  time.  Moreover,  there  is  a  wearing  action 
from  slippage  of  bucket-bottom  on  tumbler-face  (caused  by  grit) 
such  that  if  an  even  relation  between  bucket-bottoms  and  wear- 
ing-plates existed,  the  life  of  the  former  would  be  materially 
shortened  at  a  greatly  increased  annual  expenditure. 

On  screens  the  ordinary  repairs  may  be  done  during  clean-up 
time,  and  this  should  also  be  utilized  in  making  all  other  repairs 
that  are  possible. 

The  relative  value  of  the  belt-conveyor  as  against  the  pan- 
stacker  for  removing  the  coarse  oversize  from  the  screens  to  the 
stack-pile,  has  been  already  touched  upon.  A  few  interesting 
records  of  the  relative  wear  of  belts  are  available. 

On  the  two  boats  at  Oroville  several  varieties  of  belt  were 
used,  the  life  of  which  are  given  herewith  :* 

Time  of  Wear 
Name  of  Belt  Days 

Robins  belt  (Robins  Conveying  Belt  Co.) 226 

Bowers  Rubber  Belt   (Bower  Rubbers   Co.) 219 

tWest   Coast  rubber  belt 320 

Gutta  Percha  Rubber  &  Mfg.  Co. . 174 

Link  Belt  (Manhattan  Rubber  Co.) 112 

Gardner  Belt  (Boston  Woven  Hose  &  Rubber  Co.) 252 

"       287 

330 

"Information  from  W.  S.  Noyes. 
fUsing  two  pad  belts. 

On  El  Oro  a  Peerless  belt  was  in  use,  with  pad  belts,  for  18 
months : 

Days. 

Ran  without  a  pad    150 

With  6-ply  ordinary  16  in.  drive  belt 17 

With  special  pad  $£  in.  thick  with  ^  in.  rubber  on  each 

side,   16  in.   wide    137 


COSTS.  155 

Days. 

*16  in.    Candy  belt    26 

tBalata  belt,   16  in 150 

*Canvas    (soaked   in    oil),    contracted   in    width   and    stretched   in   length. 
tAn   English   belt — worn   so  thin   finally   that  lacings   could  not   be  kept   in. 

The  cost  of  labor  and  material  for  the  pan-stacker  on  the 
Exploration  No.  i  at  Oroville  for  the  twelve  months  ending  January 
1,  1905,  was  $2019,  while  for  the  previous  year  it  was  only  $1241. 
Mr.  James  H.  Leggett  states  that  on  his  5  cu.  ft.  boat  the  annual 
cost  of  maintenance  of  the  pan-conveyor  is  between  $300  and 
$500.  On  the  Syndicate  dredge  at  Folsom  the  labor  of  repairing 
the  pan-stacker  cost  an  average  of  $10  per  day. 

A  new  application  to  dredges  in  the  way  of  conveyor-belts  is 
che  Ridgway,  which  is  being  tested  on  Yuba  No.  4,  and  consists 
of  an  inside  canvas  belt  with  curved  wooden  blocks  or  carriers, 
in  which  runs  the  upper  belt  that  carries  the  material.  A  double 
driving  gear  is  used  with  motor  at  the  outboard  end  of  the  stacker- 
ladder.  On  the  shafting  of  the  drums  of  each  belt  is  a  different 
sized  gear-wheel  run  by  the  same  pinion  and  arranged  so  that 
they  run  at  the  same  speed,  and  slipping  (of  one  belt  on  the 
other)  is  obviated.  A  new  belt  is  being  introduced  on  the 
dredges,  which  it  is  claimed  will  give  superior  wear.  The  belt 
is  driven  full  of  staples,  which  are  clinched  on  the  carrying  side 
of  the  belt,  and  arranged  in  rows  that  break  joint.  It  is  said  that 
this  will  give  extra  strength  as  well  as  durability. 

Cases  of  broken  spuds  are  comparatively  few,  but  it  is  doubt- 
ful whether  the  practice  in  use  at  the  Champlin  dredge  at  Footes 
creek  in  Oregon  might  not  be  of  benefit  in  the  Sacramento 
valley.  Here  it  was  found  cheaper  to  make  both  spuds  of  wood; 
when  one  breaks  it  is  simply  exchanged  for  another,  and  the  great 
loss  of  time  entailed  in  repairing  a  broken  steel  spud  is  obviated. 
Of  course,  suitable  sticks  must  be  kept  on  hand  and  ready  for 
immediate  use.  In  some  hard  ground,  however,  wooden  spuds 
would  be  entirely  out  of  the  question. 

Modern  dredges  are  equipped  with  steel  traveling  cranes  at 
several  positions  on  the  boat,  and  these  are  almost  indispensable 
in  the  great  saving  of  time  over  the  use  of  blocks  or  in  rigging 
a  temporary  derrick  every  time  a  repair  or  replacement  of  any 
consequence  is  to  be  made. 

It  has  been  stated  by  one  writer  on  dredging  that  records 
of  lost  time  and  costs  for  the  first  few  years  on  a  dredge  should 


156 


DREDGING   FOR    GOLD   IN   CALIFORNIA. 


not  be  taken  as  accurate.  This  point  has  been  emphasized  unduly 
by  several  dredging  critics.  As  a  matter  of  fact,  though  the  average 
over  a  long  period  is  a  better. criterion  of  the  cost  of  operating,  as 
would  be  the  case  in  any  other  industry  or  business,  if  breakages 
are  honestly  repaired  at  the  proper  time  and  in  an  up-to-date 


Fig.  90.     Ladder  Hoist  on  the  Baggette. 

manner,  a  record  at  the  end  of  the  second  year  should  be  fairly 
accurate.  For  instance,  nowadays  mosfc  of  the  parts  subject  to 
constant  breakage  are  generally  sectionalized  to  such  an  extent 
that  the  actual  wearing  parts  may  be  replaced  separately,  and  the 
entire  machinery  and  plant  of  a  dredge  might  at  the  end  of  five 


COSTS.  157 

years  be  actually  better  than  at  any  time  previous ;  it  might  have 
been  necessary  to  entirely  renew  every  part  during  the  fifth  year, 
seme  of  them,  of  course,  having  been  renewed  several  times  before. 
Moreover,  the  material  used,  the  workmanship,  and  the  design 


Fig.  91.     Showing  Wear  on  Lips  of  El  Oro  Buckets. 

would  all  be  subject  to  improvement  during  the  five  years'  ex- 
perience. The  only  part  of  the  dredge  that  might  have  shown  wear 
at  that  time  would  be  the  hull,  but  these,  in  modern  dredges  are 
staunchly  built  and  in  such  a  manner  that  they  may  outlast  the 
area  over  which  they  are  designed  to  operate. 


158         DREDGING   FOR   GOLD   IN   CALIFORNIA. 

An  important  element  in  the  saving  of  time,  and  therefore  in 
cutting  down  operating  costs,  is  the  presence  of  good  railway  con- 
nections and  the  nearness  of  facilities  for  making  repairs.  At 
Oroville  there  are  several  shops  of  different  capacity,  in  some  of 
which  practically  all  the  work  required  on  a  boat  may  be  done, 
except  the  manufacture  of  castings.  These  shops  are  owned  by 
the  several  companies,  some  of  which  do  custom  work  as  well. 
The  Boston  shops  are  the  largest,  and  are  well  fitted  for  repair 
and  construction  work,  in  fact,  for  several  years  they  have  been 
constructing  the  boats  of  their  company,  both  at  Oroville  and  on 
the  Yuba.  The  equipment  consists  of  two  traveling  cranes,  an 
air-compressor,  60  by  60  in.  Detrick  &  Harvey  open  side  planer, 
6  by  6  ft.  Cincinnati  planer,  four  radial  drills  of  Varying  sizes, 
horizontal  boring  mill,  shaper,  double  traverse  head  shaper,  8-in. 
pipe  machine,  6-in.  pipe  machine,  lathes,  grinders,  small  tools, 
etc.  The  equipment  also  includes  a  steam  hammer,  cut-off 
shears,  oil  furnace  for  heating  plates,  blacksmith  shop  with  seven 
fires.  Also  a  very  complete  line  of  pneumatic  tools,  chipping 
hammers,  riveting  hammers,  drills,  etc.  A  notable  feature  of  the 
equipment  is  a  compressor  and  motor  mounted  on  a  wagon  and 
fitted  with  air  hose  and  complete  equipment  of  pneumatic  tools, 
which,  in  case  of  trouble,  may  be  quickly  hauled  to  a  dredge  to 
facilitate  repairs.  The  shops  cover  an  area  80  by  160  feet. 

The  larger  repairs  on  the  Yuba  dredges  are  done  at  the  Boston 
shops,  and  minor  work  at  their  own  temporary  shops  at  Hammon 
City.  These  will  soon  be  equipped  with  a  steam-hammer,  hydraulic 
press,  large  forges,  radial  drill,  a  compressor-plant,  and  lathes, 
etc.  Arrangements  are  also  being  made  for  the  erection  of  exten- 
sive shops  at  Marysville,  which  will  be  so  fully  equipped  that  a 
dredge  may  be  entirely  constructed  there. 

At  Folsom,  the  Folsom  Development  Co.,  has  the  largest  and 
most  elaborately  equipped  machine-shops  for  this  work  in  the 
State,  outside  of  San  Francisco,  and  every  possible  repair  (except 
castings)  is  expeditiously  made  here.  In  their  store-rooms,  it 
is  aimed  to  keep  an  adequate  stock  of  all  articles,  the  ordering 
of  which  at  a  distance  would  entail  delay  in  shipment.  Weekly 
reports  are  made  to  the  business  office  of  the  stock  on  hand  so 
that  replacements  can  be  quickly  made.  The  necessity  for  this 


COSTS.  159 

can  be  understood  when  it  is  stated  that  it  often  takes  seven  and 
eight  months  to  fill  orders  for  some  of  the  larger  castings. 

A  vivid  illustration  was  presented  at  Oroville  only  a  month 
ago,  of  loss  on  account  of  not  having  parts  on  hand.  A  5-cu. 
ft.  bucket  boat  broke  an  upper  tumbler  shaft,  which  had  to  be 
sent  to  San  Francisco  for  repair.  Over  four  weeks  were  consumed 
before  the  boat  was  running  again,  and  during  this  time  a  large 
proportion  of  the  fixed  charges  went  on,  as  well  as  interest,  and 
no  income  was  available.  Two  days  at  the  outside  are  all  that 
would  have  been  necessary  had  a  spare  shaft  been  kept  on  hand,  and 
the  interest  on  the  money  so  expended  would  be  small  compared 
with  the  loss. 

The  fixed  costs  of  dredging  include  office  management  and 
bullion  charges,  labor,  power,  water,  taxes,  insurance  and  interest, 
and  probably  50  to  60%  of  the  total  operating  cost  per  yard. 

The  bulletin  published  by  the  California  State  Mining  Bureau 
contains  many  instances  of  cost,  principally  in  the  Oroville  district, 
and  quotes  a  table  contained  in  a  paper  read  before  the  California 
Miners'  Association  by  Mr.  L.  T.  Hohl  which  I  append. 


*Costs  of  dredging  at  Oroville   (in  cents) 


Item 
Power    

No.  1 
1.06 

No.  2 

1.20 

No.  3 

1.15 

No.  4 

1.61 

No.  5 

1.77 

Repairs 

.      '   2.86 

3.03 

3.46 

2.97 

3.80 

Labor 

.1  64 

1  32 

1.85 

2.33 

2.05 

General    expenses 

064 

067 

123 

1.28 

0.73 

Total    .  ..6.20        6.72        7.69        8.19        8.35 


Whether  these  include  the  expenses  of  office,  managements, 
taxes,  interest,  insurance,  which  in  many  of  the  other  cases  given 
seem  relatively  very  small,  is  not  stated. 

It  seems  to  be  conceded,  however,  by  the  best  practical  dredge- 
men  that  the  average  cost  per  yard  at  Oroville  for  a  year's  work 


'These    referred   to    operations    several    years    ago. 


160         DREDGING   FOR   GOLD   IN   CALIFORNIA. 

does  not  get  much  lower  than  6l/2  to  7c.  Indeed,  I  am  aware 
of  at  least  one  instance  during  the  past  year  where  the  cost  ex- 
ceeded 12c.  It  is  probable,  too,  that  the  yardage  value  of  much 
of  the  ground  has  been  quoted  too  high.  The  following  costs  are 
for  the  Exploration  No.  I  for  two  consecutive  years.  It  must  be 
borne  in  mind,  however,  that  this  boat  is  somewhat  out  of  date, 
and  not  of  large  capacity. 

For  year  ending  For  year  endinp 

Item  Jan.  1,  1904.  Jan.  1.  1905. 

Cents  per  cubic  yard. 
Labor 

Operative     1.37  1.29 

Repairs     0.61  0.94 

Superintendent     0.38  0.38 

Power 

Dredge    1.08  1.00 

Pumps    0.07  0.01 

Hardware 

Supplies  and  tools,  etc 0.32  0.22 

Repair  parts  2.32  1.37 

Freight  and  express    0.04)  0.10 

Hauling 0.07^ 

Steel  cables   0.07  0.07 

Lumber 0.03  0.006 

Electrical  supplies   0.005  0.06 

Clearing    ground 0.095  0.16 

Sundry  expenses    0.02  0.007 

General  plant .  .0.24  0.26 

Bullion   expenses    0.04  0.05 

Prospecting    0.12 

General  expense 

Oroville    0.38  /  0.36 

San  Francisco   0.17  ) 

Taxes  warehouse,  insurance,  legal   ....0.28  0.77 


Total    7.71  7.06 

While,  for  the  two  years  the  total  costs  are  close,  the  monthly 
total  costs  per  yard  varied  between  4c.  and  14c.  This  dredge  cost 
$45,000  and  dredged  in  1903,  474,610  cu.  yd,  and  in  1904,  493,150 
cubic  yards. 


COSTS. 


161 


For  the  past  20  months  the  Lava  Beds  No.  3  of  the  Oro, 
Light,  Water  &  Power  Co.  has  dug  an  average  of  86,330  cu.  yd. 
per  month  at  an  average  total  cost  of  4.77  cents  per  yard. 

The  total  costs  per  cubic  yard  for  the  six  boats  of  the  Feather 
River  Exploration  Consolidated  for  the  five  months  ending  May  31, 
1906,  were  as  follows : 

Cost  in  Cents  Per  Cubic  Yard. 


Month 

Boats 

January  

No-  1 

No.  2 

No.  3 

No.  4 

No.  5 

No.  6 

3.91 
4.86 
4.44 
4.52 
5.76 

5.16 
5.15 
6.70 
4.60 
9.61 

5.88 
2.41 
3.13 
2.73 
4.71 

10.06 
9.72 
4.35 
15.52 

5.50 

4.15 
5.82 
2.79 
2.82 
5.93 

3.70 
4.55 
4.39 
4.33 
5.13 

February  

March 

April  .  .        

May  

No.  i  is  a  Risdon  boat  of  3^  cu.  ft.  bucket  capacity.  No. 
2,  j,  4  and  5  are  also  of  Risdon  construction  with  5-ft.  buckets,  and 
No.  6  is  a  Bucyrus  with  a  close-connected  5-cu.  ft.  bucket  line. 

Probably  at  Folsom  and  on  the  Yuba  the  best  work  is  being 
done  in  dredging  today.-  Assisted  by  the  examples  of  others' 
mistakes,  and  by  the  development  at  Oroville  and  elsewhere,  boats 
of  huge  capacity  have  been  constructed.  This  has  been  accom- 
plished after  careful  study,  with  every  possible  precaution  that  the 
present  stage  of  the  practice  can  suggest,  at  the  company's  own 
shops,  and  under  the  direction  of  their  own  engineers.  The  result- 
ing machines  actually  dig  from  100,000  to  over  200,000  cu.  yd.  per 
month. 

At  Folsom  cheap  power  comes  into  play,  and  the  cost  being  only 
.65c.  per  kilowatt  hour,  a  saving  is  at  once  effected  of  over  one-half 
the  power  cost  at  Oroville,  equal  probably  from  one-third  to  two- 
third  cents  per  cubic  yard. 

By  proper  organization  and  office  management,  thorough 
facility  for  repairs,  and  the  following  of  a  well  planned  system, 
expense  may  be  reduced.  An  important  element  in  this  reduction 
is  the  operation  of  as  many  boats  as  possible  under  one  manage- 
ment. One  general,  departmental,  assay,  and  other  offices,  one 


162 


DREDGING   FOR    GOLD   IN   CALIFORNIA. 


repair  plant  and  store-house,  with  a  reduced  number  of  heads  of 
departments  and  employees  will  cut  down  the  salary,  building, 
and  maintenance  accounts  immensely.  Labor,  of  course,  is  one 
of  the  important  fixed  charges  in  dredging.  .  Usually  three  shifts 
are  employed,  and  the  regular  crew  consists  of  a  dredgemaster, 
winchmen,  and  two  oilers.  The  wages  are  as  follows : 


District 

Foreman  or 
Dredgemaster 

Winchman 

Oilers 

Other  Lahor 

Oroville  
Yuba 

Per  Month 
$125 

$150 

Per  Shift 
$3.00 

$4  00 

Per  Shift 

$2.50 
$3  00 

Per  Shift 

$2.00 

$2  50 

Folsom 

1150 

$3  50 

|2  75 

$2  50 

Special  labor  is  sometimes  required  at  the  clean-up,  on  repair 
work,  and  always  in  clearing  the  ground,  blasting,  prospecting,  etc., 
and  all  this  must  be  added  to  the  annual  yardage  cost  in  computing 
the  profit. 

The  cost  of  power  is  more  or  less  fixed,  but  it  may  be  reduced 
by  care  and  the  use  only  of  the  most  improved  forms  of  motors, 
cables,  winches,  and  driving  gear,  etc. 

The  cost  of  water  is  not  such  an  important  item  and  depends 
entirely  on  the  local  conditions.  Ingenuity  in  the  use  of  stream 
and  river  water  may,  however,  save  the  purchase  of  many  inches 
of  irrigation  water.  On  the  Yuba  the  only  difficulty  in  this  connec- 
tion is  in  pumping  water  out  of  the  ponds,  as  the  seepage  gives  the 
required  supply. 

By  referring  to  the  tables  of  cost,  the  relative  expense  of  power 
may  be  deducted.  The  cost  at  Oroville  is  l^c.  per  kilowatt  hour, 
the  horse-power  used  varying  from  60  to  275  per  boat.  The 
nominal'  horse-power  may  be  obtained  from  the  detailed  description 
of  boats  given  under  Chapter  VIII. 

[Further  details  of  cost  are  given  in  the  Appendix.] 


VII.    THE  HORTICULTURAL  QUESTION. 

Much  has  been  said  and  written  since  dredging  commenced 
in  earnest  in  the  Sacramento  valley  on  the  question  of  the  des- 
truction of  the  land  by  rendering  it  unfit  for  future  agricultural 
purposes,  chiefly  fruit  culture.  A  large  portion  of  this  matter, 
particularly  that  which  has  appeared  in  certain  popular  magazines, 
is,  to  say  the  least,  misleading.  Efforts  have  actually  been  made 
to  restrain  companies  from  carrying  on  their  operations.  No 
apology  therefore  is  needed  in  referring  to  this  subject.  Care 
has  been  taken  to  obtain  the  facts  from  persons  interested  both  in 
dredging  and  in  the  culture  of  fruit,  and  the  following  brief  remarks 
sum  up  the  results  of  such  investigation. 

Oroville  is  the  most  important  district  in  this  connection  and 
here  the  possible  dredging  lands,  including  what  have  already  been 
worked,  will  probably  cover  about  6000  acres.  Of  this  tract  less 
than  400  acres  has  been  planted  in  fruit  and  though  about  1000 
acres  of  the  remaining  portion,  at  an  outside  estimate,  might,  with 
irrigation,  be  used,  it  is  ground  of  a  poorer  quality,  requiring  much 
annual  expense  in  water  and  cultivation,  and  it  is  extremely  doubt- 
ful, judging  by  the  prevailing  conditions,  whether  it  would  ever 
be  used  for  this  purpose.  Of  the  400  acres  mentioned,  150  acres 
are  included  in  the  Leggett  vinery,  which  for  several  years  has 
been  infested  with  the  practically  fatal  phylloxera  and  probably 
$300  per  acre  would  cover  the  amount  on:  which  it  would  pay,  say 
6%  per  annum,  for  horticultural  purposes.  Similarly,  the  Wilcox 
peach  orchard,  covering  50  acres,  produced  an  average  of  one  crop 
in  three  years,  and  might  provide  an  income  of  6%  on  $100  per 
acre.  The  Gray  peach  orchard  of  20  acres  would  pay  a  fair  rate 
of  interest  on  $200  an  acre.  The  Gardella  tract  is  a  fine  piece  of  land 
of  40  acres  and  peculiarly  adaptable  for  the  production  of  vegetables 
as  well  as  fruit,  and  for  market  gardening  generally,  and  would 
possibly  pay  6%  on  $1000  per  acre.  The  remaining  portion  cannot 
be  valued  at  over  $50  per  acre,  and  the  whole  6000  acres  would  not 
represent  at  the  outside  an  invested  capital  of  over  $250,000.  More- 
over it  is  a  well-known  fact  that  most  of  the  ranches  in  this  district 
were  mortgaged. 

If  we  say  that  the  district  will  yield  on  the  average  lOc.  per  yd. 


THE   HORTICULTURAL    QUESTION.  165 

net  profit  and  averages  eight  yards  in  depth,  both  fairly  conservative 
estimates,  then  over  twenty-three  million  dollars  net  profit  will 
be  produced  and  if  invested  in  the  State  at  6%,  will  produce 
an  annual  income  of  over  $1,380,000  instead  of  the  paltry  revenue 
of  $15,000  per  year,  which  the  land  produced  before.  Besides 
this  for  a  long  period  a  large  population  will  be  employed  in  the 
district  and  at  the  end  of  the  period  of  operation  another  twenty 
million  dollars  should  have  been  expended  in  labor  and  machinery. 

On  the  Yuba  the  question  of  interference  with  arable  land 
does  not  arise. 

At  Folsom  most  of  the  bench  land  has  been  worked  over  before 
by  gravel  miners,  who  left  a  large  proportion  of  it  in  such  a  con- 
dition that  it  is  unfit  for  cultivation.  Of  the  6000  acres  available 
for  dredging,  probably  not  over  5%  has  been  planted  and  little 
more  is  available  for  planting,  the  chief  product  being  grapes. 
This  land  is  owned  by  the  Natoma  Vineyard  &  Winery  Co.,  and 
the  population  it  actually  supports  is  small.  A  comparison 
similar  to  that  at  Oroville  might  be  made  out  regarding  this  district, 
which  would  probably  show  even  less  favorable  results  for  those 
busybodies  and  other  uninterested  parties  who  have  attempted 
by  unwarranted  agitation  to  raise  a  storm  in  a  tea  cup.  If  the 
question  be  really  pushed  to  an  issue,  an  excellent  solution  would 
be  to  invest  enough  of-  the  proceeds  of  the  dredging  operations 
in  the  filling  of  the  now  worthless  tule  lands  (of  vast  extent  in 
this  valley),  so  that  an  acreage  equal  to  that  destroyed  might  be 
put  into  cultivation.  This,  however,  would  probably  be  an  incon- 
siderable sum,  particularly  as  the  sale  of  such  land  would,  of  course, 
revert  to  the  dredging  companies. 

After  dredging  the  land  is  covered  with  stack  piles  containing 
boulders  and  pebbles,  the  fine  material  being  hidden  6  to  15  ft. 
below.  In  regard  to  the  reclamation  of  land  in  this  condition, 
certain  experiments  attempted  by  Mr.  J.  H.  Leggett  at  Oroville, 
produced  interesting  results.  Eucalyptus  of  both  the  'blue'  and 
the  'red  gum'  variety  and  some  fig  trees  were  planted  on  the  stack 
piles,  and  alfalfa  grass  is  also  growing.  The  trees,  when  set  out, 
were  only  about  10  in.  high.  Fig.  93  shows  the  results  at  the  end 
of  two  years.  In  the  case  of  the  largest  tree,  19  ft.  of  growth 
was  attained  and  of  course  this  will  increase  in  greater  proportion 
with  time.  Some  of  these  trees  were  planted  directly  on  top  of 


166 


DREDGING   FOR   GOLD   IN   CALIFORNIA. 


the  highest  ridges,  15  ft.  above  the  original  surface  and  Mr.  Leggett 
states  that  one  cannot  dig  a  hole  at  any  of  these  highest  points 
more  than  2  ft.  without  getting  moisture,  even  in  the  driest 
time  in  summer.  The  volcanic  ash  that  forms  the  bottom  of  the 


Fig.  93.     Eucalyptus  Two  Years  After  Being  Planted  on  a 
Stack  Pile.     19  Feet  High. 

digging  and  the   material   of  certain  clay  bands   is   often  carried 
over  the  stacker  in  lumps  and  disintegrates  on  being  exposed  to 
the  air  so  as  to  form  the  soil  necessary  to  growth.      The  alfalfa 
roots   were   accidently   thrown   up   by   the    dredge   and   the   grass 


THE   HORTICULTURAL    QUESTION. 


167 


Fig.  94.     Eucalyptus  Just  Planted  on  Stack  Pile. 
8  Inches  High.     See  Pipe. 

seems  to  do  particularly  well.  Absolutely  no  care  was  given  to 
the  trees  or  grass  from  the  time  they  were  set  out. 

Nevertheless,  with  the  stack  piles  in  their  present  condition  of 
irregular  surface,  it  is  not  considered  that  a  profitable  horticultural 
industry  could  be  built  up.  It  has  been  suggested  that  the  piles 
might  be  leveled  with  huge  scraping  rakes  run  by  electric  power, 
and  in  this  connection  an  instance  of  the  present  cost  by  hand  for 
leveling  at  Oroville  is  given.  Near  the  town  the  original  owner 
of  a  tract  that  was  dredged  agreed  to  put  the  ground  in  a  suitable 
state  of  cultivation  if  given  to  him.  He  leveled  one  acre  and  covered 
it  with  one  foot  of  soil  and  now  has  a  productive  garden;  the  total 
cost  of  leveling  and  covering  being  $250. 

Ground  that  was  dug  by  the  single-lift  dredges  (with  the  long 
sluice  on  a  pontoon  to  the  rear)  was  left  in  as  good  condition  as 
before  dredging  commenced,  that  is,  for  agricultural  purposes.  It 
is  perfectly  flat  and  the  fine  tailing  is  mixed  with  the  pebbles  and 
boulders,  and  in  many  cases  is  altogether  on  top.  Instances  of 
this  may  be  seen  where  the  Continental  dredge  operated  at  Oro- 
ville, and  at  Folsom  a  particularly  good  example  is  afforded  by  the 


168         DREDGING   FOR   GOLD   IN   CALIFORNIA. 

work  of  the  Ashburton.  This  boat  originally  employed  the  long- 
sluice  method,  but  changed  to  the  ordinary  screen  and  -tables,  and 
the  contrast  between  the  two  results  in  stacking  may  be  observed 
on  the  same  property,  the  work  having  been  done  by  the  same 
dredge. 

At  Folsom  the  stack  piles  are  to  become  a  valuable  asset  in 
the  hands  of  the  enterprising  management  of  the  Folsom  Develop- 
ment Co.,  who  are  installing  a  rock-crusher  plant  and  the  product 
is  to  be  used  in  railway  and  road  ballast,  and  for  concrete  work. 


VIII.      GENERAL. 

A  few  brief  descriptions  of  each  district  in  regard  to  the  num- 
ber of  companies  and  boats  in  each,  nature  and  value  of  ground, 
etc.,  are  given  below. 

There  are  sixteen  companies  now  engaged  in  dredging  at  Oro- 
ville and  thirty-two  dredges  are  operating,  as  follows : 

No.  of 
Name  of  company  Boats  Builders 

American  Gold  Dredging  Co 2  Bucyrus. 

Butte   Gold  Dredging  Co 1  Bucyrus. 

El   Oro   Dredging  Co 1  Link  Belt 

Machinery   Co. 

Feather  River  Exp.  Con.  Co 5  Risdon. 

1  Bucyrus. 

Gold  Run  Dredging  Co 1  Bucyrus. 

Indiana  Gold  Dredging  &  Mining  Co 2  Bucyrus. 

Leggett  Gold   Dredging  Co 1  Risdon. 

Nevada  Gold  Dredging  Co 1  Bucyrus. 

Ophir  Gold  Dredging  Co 1  Bucyrus. 

Oro  Water,  Light  &  Power  Co 1  Risdon. 

"     3  Bucyrus. 

Oroville  Dredging,  Ltd 4  Risdon. 

3  Bucyrus. 

3  Marion  Steam 

Shovel    Co. 

Oroville  Dredging  Co -. 1  (dipper)     " 

Pennsylvania  Dredging  Co 1  Golden   State   & 

Miners'  Iron  Works. 

Pacific   Dredging   Co 1  Bucyrus. 

Viloro  Syndicate 1  Bucyrus. 

Formerly  this  district  was  one  of  the  most  important  placer 
camps  in  the  State,  the  second  discovery  of  gold  having  been  made 
a  few  miles  above  the  present  site  of  the  town  in  1848  by  John 
Bidwell.  The  richest  portion  of  the  gravel  having  been  worked 
over  by  white  men,  Chinese  took  their  place  and  swarmed  over  the 
ground,  working  the  same  claims  over  again  in  many  instances. 
In  fact  it  is  these  very  portions,  already  worked  over  several  times, 
that  now  give  the  highest  returns  on  the  dredges.  It  is  generally 
supposed  that  the  Chinese  did  not  work  below  the  water  level  but 
in  many  cases  there  is  abundant  evidence,  both  in  the  drilling  and 


172          DREDGING   FOR    GOLD   IN   CALIFORNIA. 

dredging  operations,  that  they  did.  Old  workings  are  frequently 
encountered  in  drilling  and  timbers  from  these  tunnels  and  wing- 
dams,  etc.  are  often  brought  up  by  the  dredges.  The  Chinese 


Fig.  97.     Old  Chinese  Workings  at  Folsom,  showing  Home-Made 
Water- Wheel  for  Chinese  Pump. 

pump  was  employed  and  actuated  either  by  a  small  local  water 
power  or  by  hand.  This  contrivance  consisted  of  one  or  two 
3-in.  belts  with  blocks  of  wood  attached  as  elevators,  and  a  home- 
made water-wheel,  with  board  launder  from  an  irrigation  ditch 


GENERAL. 


173 


jr  stream,  completed  the  plant.  Fig.  97  shows  a  typical  Chinese 
plant  as  seen  today,  in  ground  worked  over  years  ago  and  probably 
to  be  worked  again,  by  the  dredges. 

At  Oroville  I  saw  a  link  with  the  past.     Within  sight  and  hear- 
ing  of   the    creaking    and    groaning    dredges,    sheltered    from   the 
summer  sun  by  a  few  boards,  sat  an  old  man  from  the  Oddfellows 
home  nearby — a  relic  of  the  days  of  '49.      He  was  working  a  rocker 
and  an  occasional  trip  with  a  wheelbarrow  to  the  neighboring  bank 


Fig.  98.     Gravel  Bank  at  Oroville. 

would  provide  him  with  gravel  for  most  of  the  day.  Though  far 
from  communicative  I  learned  that  he  had,  during  the  fine  days  of 
summer  in  the  past  three  years,  driven  the  little  tunnel  shown  in 
the  accompanying  illustration.  It  was  only  about  8  or  9  ft.  long 
and  during  that  period  he  had  washed  some  13  or  14  cu.  yd.  of  gold- 
bearing  gravel. 

The  gravel  in  this  district  is  from  18  to  40  ft.  deep  and  averages 
about  30  ft. ;  the  bore-hole  sections  given  under  'Prospecting' 
will  give  an  idea  of  its  composition.  The  bottom  of  the  dredging 


174 


DREDGING   FOR   GOLD   IN   CALIFORNIA. 


ground  is  generally  a  volcanic  ash,  quite  soft,  but  often  found  to 
be  tough  and  elastic  in  dredging.  As  to  gold  being  contained  in 
appreciable  quantities  below  the  present  digging  level,  as  has  been 
stated  by  some  writers,  the  result  of  the  deep  bore-hole,  already 
quoted,  speaks  for  itself.  It  is  not  known  that  any  gold-bearing 
stratum  of  any  consequence  lies  underneath  the  level  to  which  dig- 
ging is  being  carried  in  this  district  and,  contrary  to  general  sup- 


Fig.  99.     An  Old  Miner  and  His  Rocker. 

position,  the  gold  in  the  gravel  is  not  evenly  disseminated  from  top 
to  bottom  over  the  entire  district.  It  would  indeed  be  an  extra- 
ordinary case  if  it  were  so.  (See  'Prospecting.') 

It  would  be  a  difficult  matter,  with  the  present  lack  of  infor- 
mation and  the  unwillingness  of  the  dredge-owners  to  make  it 
public,  to  give  correctly  the  average  value  of  the  gravel  per  yard, 
either  in  this  or  the  other  districts.  It  has  been  variously  stated 
to  average  from  15  to  25c.  per  cu.  yd.,  and  probably  a  correct 
average  would  fix  it  much  nearer  the  former  figure  than  the  latter, 
for  the  whole  6000  acres.  This  figure  depends  of  course  upon 
whether  the  "prospect"  or  "recoverable'  value  is  taken,  the  latter 


GENERAL.  175 

• 

being,  as  a  rule,  considerably  lower  than  the  former.  In  an  area 
of  some  560  acres,  175  holes  gave  an  average  result  of  14c.  per 
cu.  yd.  Another  tract  of  200  acres  near  the  town  of  Oroville 
prospected  an  average  of  36c.  per  cu.  yd.,  while  an  adjoining  pro- 
perty of  over  100  acres  was  said  to  average  28c.  The  ground  near 
the  town  of  Oroville  appears  to  be  fairly  rich,  while  the  tracts  at 
the  extreme  southern  end  of  the  district  are  generally  of  lower 
grade,  but  the  character  of  the  .ground  renders  it  easier  to  dredge. 
Consequently  the  cost  at  the  southern  properties  have  been  as  low  as 
3c.  per  cubic  yard. 

The  power  used  is  entirely  electric  and  is  controlled  by  the 
California  Gas  &  Electric  Co.,  which  has  dams,  ditches,  and  power 
plants  at  several  points  in  the  higher  foothills.  A  good  irrigation 
system  exists  and  supplies  water  where  necessary. 

A  brief  description  of  some  of  the  boats,  including  the  newest 
and  oldest  of  each  type,  at  Oroville,  will  give  an  idea  of  the  differ- 
ence in  design. 

The  housing  of  the  earlier  Risdon  boats  usually  had  pitch 
roofs  and  the  trommel  and  gold-saving  tables  were  not  housed  in. 
An  example  is  the  Exploration  No.  i.  The  hull  is  86  ft.  long  by 
30  ft.  wide,  and  7  ft.  deep.  The  bucket-line  was  originally  open- 
connected  with  buckets  of  4-cu.  ft.  capacity.  This  has  been 
changed  to  a  close-connected  line  of  78  buckets,  each  of  3- 
cu.  ft.  capacity.  The  ladder  is  made  up  of  plate  and  angle-iron 
girder  sides  with  bulkhead  plates  and  lattice  bars  between.  The 
trommel  screen  is  25  ft.  in  length  and  4  ft.  6  in.  diam. ;  the  gold- 
saving  tables,  12  in  number,  slope  from  the  screen  toward  each 
side,  emptying  into  a  stream-down  sluice.  Angle-iron  riffles  are 
used.  The  stacker  is  composed  of  a  pan-conveyor  and  the  boat 
works  on  a  head  line. 

The  latest  Risdon  boat  built  is  the  Baggette.  The  hull  is  98  ft. 
long  by  34  ft.  wide.  The  ladder  is  of  truss-girder  design  and  the 
open-connected  buckets,  of  which  there  are  39,  hold  7  cu. 
ft.  each.  The  upper  tumbler  on  all  Risdon  boats,  is  square 
and  the  lower  tumbler  is  pentagonal.  The  middle  gauntree  is 
built  of  iron,  but  instead  of  the  usual  design — battered  fore  and 
aft — the  back  is  vertical,  thus  giving  more  room  aft  for  the  screening 
apparatus.  An  improvement  has  been  made  also  in  the  driving 
gear.  It  has  always  been  held  by  some  that  the  use  of  a  large 


176          DREDGING   FOR    GOLD   IN   CALIFORNIA. 

gear-wheel  on  one  side  with  a  small  pinion  below  is  a  source  of 
trouble  and  weakness,  particularly  as  the  bearings  of  gear-wheel  and 
pinion  rest  on  separate  castings.  This  has  been  obviated  in  the 
Baggette,  and  the  pinion  is  more  nearly  to  one  side  of  the 
gear-wheel,  and  in  the  same  casting.  A  new  arrangement  was 
tried  for  hoisting  the  ladder.  The  motor  was  placed  at  the  head 
of  the  forward  gauntree  and  two  chains  running  over  sprockets  were 
used,  the  ends  of  the  chains  dropping  into  the  hold.  It  was 
found  not  to  be  a  success  and  it  was  replaced  with  a  sheave- 
wheel  arrangement,  similar  to  the  ordinary  ladder-hoist.  The 
screen  is  29  ft.  6  in.  long  and  6  ft.  diam.  and  both  it  and  the  gold- 
saving  appliance  have  been  thoroughly  described  in  Chapter  VI. 
The  motors  are  as  follows : 

Purpose  Horse-power 

Main    drive    or    digging 75 

Ladder  hoist    35 

Pumps 50 

Priming    pump    5 

Screen     20 

Stacker     15 

Winches     20 

Total     220       4 

The  boat,  like  all  others  of  the  Risdon  type,  is  operated  on 
a  head  line.  Six  men  are  employed  on  three  shifts,  not  including 
the  dredgemaster. 

The  Boston  No.  4,  although  chiefly  built  by  the  Boston  shops 
at  Oroville,  is  a  modified  Bucyrus  type.  An  improvement  has  been 
made  in  the ,  design  of  the  forward  gauntree  frame  over  the  old 
'A'  style  and  four  parallel  upright  posts  are  used,  strengthened 
with  a  good  system  of  braces  and  securely  tied  to  the  main  framing 
of  the  boat.  The  cap  is  of  steel.  The  gauntree  slopes  forward 
at  an  angle  of  5 1\  in.  horizontal  to  1  ft.  vertical — somewhat  steeper 
than  usual.  The  digging  ladder  is  very  heavy  and  constructed 
of  plate  and  angle-girder,  the  sides  braced  with  lattice-bars  be- 
tween. The  bucket  line  consists  of  68  close-connected  buckets 
of  7^-cu.  ft.  capacity  each.  They  dig  at  the  rate  of  about  20  per 
min.  The  upper  tumbler  is  pentagonal  and  the  lower  one  hexagonal. 


GENERAL. 


177 


The  trommel  is  6  ft.  diam.  and  30  ft.   long,  28  ft.  of  which  are 
perforated.      The  gold-saving  arrangement  is  as  follows  : 

The  stacker  is  of  the  belt-conveyor  pattern  and  the  boat  is 
operated  on  spuds.  The  motors  are  of  the  following  nominal 
capacity : 


Purpose 

Make 

Horse-Power 

Main  drive  and  ladder  hoist  

Gen 

eral  Elec 

:tric 

150 

25 
50 
10 

25 
25 
75 

Low  pressure  pump  

Hio-h        "             " 

Priming                 '  ' 

Side  line  winches 

Screen,  spuds,  and  stacker  drive  .... 
Sand  pump  

Total, 


360 


On  the  Yuba  there  are  two  companies :  The  Yuba  Consolidated 
Gold  Fields  and  the  Marysville  Gold  Dredging  Co.,  the  first  with 
eight  dredges  and  the  second  with  two.  These  companies,  however, 
are  practically  under  the  same  general  management. 

The  headwaters  and  tributary  streams  of  the  Yuba  river  have 
for  years  been  mined  extensively  by  hydraulicking  and  it  is  esti- 
mated that  beside  the  natural  detritus,  carried  down  each  year  in 
the  floods,  there  have  been  300,000,000  cu.  yd.  deposited  in  the 
lower  river-bed  alone. 

Naturally  the  old  river-bed  gravel,  which  is  gold-bearing,  has 
been  covered  with  an  overburden  consisting  chiefly  of  sand  and 
'slickens'  from  the  hydraulic  workings;  this  varies  from  12  to 
30  ft.  in  depth  and  though  it  contains  some  gold,  it  is  difficult  to 
discharge  clean.  The  total  digging  depth  is  from  50  to  70  ft.  Below 
the  overburden  of  tailing  is  the  usual  'wash',  similar  to  that  of 
the  Oroville  district.  Below  this,  the  volcanic  ash  is  encountered 
and  presents  the  same  sticky  and  elastic  mass  so  difficult  to  dig 
that  forms  the  so-called  'false  bedrock'  in  the  other  districts.  Bore- 
holes below  this  showed  some  gold  down  to  115  ft.  from  the 
surface. 

With  the  exception  of  No.  i  and  No.  2  of  the  Yuba  Consoli- 
dated Gold  Fields,  the  boats  of  both  companies  are  of  the  same 
type.  No.  i  and  No.  2  have  buckets  of  6-cu.  ft.  capacity,  while 
those  of  all  the  others  are  of  7^  cu.  ft.  They  are  all  of  the 


178         DREDGING   FOR   GOLD   IN   CALIFORNIA. 

close-connected  type  and  all  the  boats  operate  on  spuds  and,  except 
No.  i  and  No.  2  (which  each  have  two  shaking  screens,  in  exten- 
sion) use  revolving  trommels.  The  most  marked  impression  a  new 
observer  receives  of  the  Yuba  practice  is  the  immense  length  of 
stacker  necessitated  by  the  great  depth  of  the  ground  dug.  A 
description  of  the  No.  7  boat  of  the  Yuba  Consolidated  Gold  Fields 
will  typify  the  best  points  in  the  others.  The  hull  is  115  by  40  ft. 
The  digging-ladder  is  of  the  open  truss-girder  design,  114  ft. 
long  and  the  bucket-line  contains  93  buckets  close-connected  and 
of  7l/2-z\\.  ft.  capacity  each.  Both  the  upper  and  lower  tumblers 
are  hexagonal  and  the  upper  tumbler-shaft  is  17  in.  diam.  at 
tumbler  and  the  journals  are  13  in.  diam.  The  trommel  is  30  ft. 
long  and  6  ft.  diam.  The  gold-saving  tables  on  both  this  boat  and 
No.  8  were  intended  to  be  on  the  Holmes  system,  but  unfortunately 
these  were  destroyed  in  the  San  Francisco  fire  while  they  were 
being  manufactured.  Accordingly,  the  old  pattern  side  tables 
with  stream-down  box,  were  put  on  No.  J  and  Holmes  tables, 
partly  wood  and  partly  of  iron,  were  improvised  for  No.  8.  It  is 
intended  later  to  change  the  tables  on  No.  7.  The  spuds  on  these 
boats  are  55  ft.  long  and  24  by  36  in.  section ;  they  are  constructed 
of  ^-in.  end  plates  and  ^-in.  side  and  web  plates  and  with  angle- 
iron  joints.  The  angle-flanges  are  4  by  4  by  \l/2  in.  thick.  The 
stacker-ladder  is  132  ft.  long  between  centres  of  drums  and  the 
conveyor-belt  is  32  in.  wide,  -Hj-in.  thick  and  174  ft.  long. 

The  ten  dredges  working  in  this  district  are  digging  the  actual 
bottom  and  are  co-operating  with  the  Debris  Commission  in  build- 
ing their  dams.  By  referring  to  the  acompanying  sketch  map 
(Fig.  100)  an  idea  of  this  work  may  be  obtained. 

The  Yuba  bottom  is  shown  by  the  enclosing  heavy  lines,  which 
represent  approximately  either  the  old  levees  or  natural  high  banks, 
and  in  winter  or  flood-time  the  area  enclosed  is  almost  completely 
covered  with  water  for  its  width  of  nearly  two  miles.  In  summer,  the 
flow  is  represented  by  several  streams  that,  constantly  changing 
their  course,  leave  bars  and  quicksands  where,  within  a  few  hours, 
the  current  was  racing.  The  main  portion  of  the  river  flows  at 
present  as  shown  in  the  sketch,  but  it  is  to  be  diverted  through 
the  cut  behind  Daguerre  Point  recently  completed  by  steam-shovel. 
The  dam,  which  is  thoroughly  described  in  the  MINING  AND 
SCIENTIFIC  PRESS  of  September  2,  1905,  is  situated  about  three  miles 


> 
I 

•— 

o 

ex 


8 


180 


DREDGING   FOR    GOLD   IN   CALIFORNIA. 


above  the  present  dredging  ground.  The  training  walls  or  clams, 
shown  by  double  continuous  and  dotted  lines,  are  being  built 
by  the  dredges  and  consist  of  the  stack  piles.  The  cut  behind 
Daguerre  Point  and  the  north  training  wall  have  been  already 
built,  as  far  as  shqwn,  by  the  Government ;  and  the  dredges  of 
both  companies  are  working  in  the  directions  shown  by  the  arrows. 
At  A  a  spillway  or  inlet  is  to  be  made ;  this  can  be  raised  or  lowered, 
so  that  the  settling  basin  in  the  low  ground  behind  Hammon 
City  may  gradually  be  filled.  At  B  is  the  outlet  to  this  settling 
basin,  which  receives  the  overflow  east  of  the  east  training  wall 
and  will  have  a  capacity  of  5,000,000  cubic  yards. 

At  Folsom  there  are  three  companies  operating  seven  boats, 
as  follows: 


Name  of  Company 

No.  of 
Boats 

Builders. 

Capacity  of 
buckets  in 
cu.  ft. 

Folsom  Development  Co. 

Ashburton  Mining  Co.  .  .  . 
Eldorado  Dredging  Co.   . 

2 
2 
1 
1 
1 

Western  Eng.  &  Construction  Co. 
Folsom  M.  Co. 
Western  Eng.  &  Construction  Co. 
Bucyrus 
Risdon 

5.8 
8.9  and  13 
8.5 
9 
6 

There  are  four  other  old  boats  in  the  district,  one  of  which 
might  be  remodeled  and  used. 

The  dredging  ground  along  the  American  river  is  composed 
of  successive  benches  and  the  bars  formed  by  the  old  courses  of 
the  river.  The  sketch  (Fig.  101^)  is  taken  from  'Report  of  the 
California  Bureau  of  Mines'  and  shows  how  the  course  of  the  river 
has  changed.  There  are  probably  some  6000  acres  in  all,  which 
may  be  dredged,  and  though  some  of  this  is  of  low  value  per 
yard  this  portion  is  generally  soft  and  easy  to  dig.  The  costs 
in  this  district  are  low. 

No'.  4  boat,  belonging  to  the  Folsom  Development  Co.,  is 
the  largest  dredge  in  the  world  and  the  following  outline  des- 
cription will  give  an  idea  of  its  size  and  equipment.  The  design 
of  the  dredge  is  a  combination  of  Bucyrus  and  Folsom  Develop- 
ment Co.'s  shops,  and  was  erected  by  the  latter.  The  hull  is 
102  ft.  long  and  58  ft.  wide.  There  are  59  buckets,  each  of  13 
cu.  ft.  capacity  and  the  digging-ladder  is  66  ft.  11  in.  long.  Both 
the  upper  and  lower  tumblers  are  hexagonal.  The  dimensions 
of  the  shaking  screens  are:  Upper  screen,  10  ft.  6  in.  by  11  ft. 


be 
£ 


182 


DREDGING   FOR    GOLD   IN   CALIFORNIA. 


11  in.  Lower  screen,  14  ft.  by  12  ft.  8  in.,  and  together  they 
contain  a  total  superficial  area  of  300  sq.  ft.  The  Holmes  system 
of  gold-saving  tables  is  used.  The  stacker  ladder  is  85  ft.  6  in. 
long  and  the  conveyor-belt  is  44  in.  wide  and  sets  of  four  idlers 
are  used. 


^*fe 


MSODLE 


Of 

Fig.  101M- 


The  motors  are  as   follows : 

Name   of  motor.  H.  P.  Description. 

Ladder  hoist  and  main  drive 150     Westinghouse  variable  speed. 

Main  pump    ,  .  . .  100  constant     " 

Auxiliary  pump 15 

Screen  drive 30 

Stacker    30 

Headline  and  sidelines 30  variable 

The  boat  is  worked  entirely  on  head  line. 


IX.    APPENDIX. 

Gold  Dredging. 

The  Editor: 

Sir — I  have  had  occasion  recently  to  inquire  into  various  as- 
pects of  gold  dredging.  I  find  that  whereas  the  purely  technical 
side  of  this  industry,  such  as  dredge  designing  and  operating,  has 
been  written  about  a  good  deal,  the  statistical  and  financial  aspects 
have  hardly  been  dealt  with  at  all. 

Let  me  enumerate  some  -questions  to  which  as  yet  I  have  not 
found  satisfactory  answers : 

1 .  How  many  payable,  or  probably  payable,  dredging  areas  are 
known  in  the  world,  and  what  is,  approximately,  their  gross  extent  ? 
Which  are  the  likeliest  countries  to  prospect  ? 

2.  How  much  gold  is  produced  yearly  by  dredges,  and  how 
much  of  the  production  is  profit  ? 

3.  How  many  dredges  are  now  working  at  a  profit? 

4.  How  many  dredges  that  were  once  worked  are  not  now 
working,  and  what  were  the  reasons  for  their  stoppage  ?    How  much 
money  do  these  represent? 

5.  What  are  the  precise  costs  in  different  localities?    How  are 
costs  affected  by 

a.  Type  of  dredge? 

b.  Nature  of  deposit? 

c.  Nature  of  power? 

d.  Climate  ? 

6.  What  is  the  best  system  of  prospecting  dredging  ground? 
How  should  such  system  be  adapted  to  different  kinds  of  ground  ?  Is 
drilling  as  effective  as  sinking  shafts  or  paddocks?     What  is  an 
average  recovery  of  the  gold  contents  as  shown  in  prospecting? 
Why  are  favorable  results  in  prospecting  often  falsified  in  practice? 

7.  Assuming  prospected  or  otherwise  proved  ground  to  repre- 
sent 'ore  blocked  out',  which  is  the  correct  basis  of  valuation  for 
such  ground? 

If  gold  dredging  is  to  be  regarded  as  a  scientific  industry,  it ' 
seems  to  me  that  satisfactory  answers  to  such  questions  as  these 
should  be  procurable.     A  mass  of  facts  must  be  available  by  now. 
Can  you  not,  through  your  many  sources  of  information,  undertake 
the  collection  of  these  ? 


184         DREDGING   FOR   GOLD   IN   CALIFORNIA. 

The  cardinal  fact  which  would  seem  to  emerge  from  my  in- 
quiries is  that  the  known  areas  of  profitable  dredging  ground  are 
not  numerous,  and  are  limited  to  a  few  countries.  When  recently 
in  San  Francisco  I  had  this  statement  indorsed  by  the  man  who,  I 
consider,  knows  more  about  gold  dredging  than  anyone  else.  He 
has  for  years  past  sent  experienced  prospectors  over  the  United 
States,  South  America,  the  East,  and  elsewhere,  but,  I  understand, 
outside  of  his  California!!  properties  has  found  nothing  definitely 
good.  Of  course,  one  must  not  jump  to  the  conclusion  that  no  more 
good  areas  will  be  found.  South  America,  Alaska,  Siberia,  India, 
and  the  Eastern  islands  still  offer  an  immense  field  for  research ; 
and,  although  ideal  dredging  conditions  cannot  exist  in  these  coun- 
tries, there  is  no  reason  why  they  should  not  contain  many  payable 
areas.  In  the  meantime,  it  may  be  taken  for  granted  that  the  defin- 
itely good  areas  are  limited.  Ideal  dredging  conditions  exist,  I 
believe,  only  in  certain  parts  of  California  and  New  Zealand,  while 
Victoria  ranks  next,  but  a  long  way  behind.  At  present  the  two 
first-named  countries  are  probably  producing  75  per  cent  of  the  gold 
won  by  this  method.  Dredging  in  the  United  States  is,  I  under- 
stand, almost  confined  to  California.  I  make  the  statement,  subject 
to  correction,  that  there  are  not  more  than  four  dredges  working 
elsewhere  at  a  profit,  and  that  outside  California  conditions  for  work- 
ing are  usually  unsatisfactory.  Several  dredges  are  said  to  be  work- 
ing at  a  profit  in  Montana,  but  I  have  found  no  one  who  can  give  me 
exact  statements.  In  California,  the  chief  centre  of  dredging  is 
Oroville,  where  the  conditions  are  quite  ideal.  A  recent  visit  to  this 
field  impressed  me  with  the  idea  that  the  Oroville  gravels — proved 
as  they  are — form  the  safest  gold  mining  venture  in  the  world.  At 
Folsom  there  are  also  good  dredging  areas,  and  Bear  River  should 
soon  become  profitable.  But  the  centre  of  interest  in  gold  dredg- 
ing will  soon  shift  to  the  Yuba  river.  Here  a  large  area  of  gravel 
90  ft.  deep  has  been  found  to  give  good  values,  and  several  dredges 
already  at  work  have  confirmed  these  results.  One  company,  alone, 
will  shortly  be  working  15  dredges,  of  a  new  and  very  powerful 
type.  The  strength  and  efficiency  of  these  is  such  that  they  will 
handle  90  ft.  of  gravel  as  easily  as  the  other  types  can  handle  30 
feet. 

In  Canada,  dredging  on  the  Eraser  and  Saskatchewan  rivers 
has  been,  somewhat  unaccountably,  a  failure  ;  I  should  like  to  know 
the  reasons  for  this.  I  should  also  like  to  have  precise  figures  about 


APPENDIX.  185 

the  dredges  working  at  Atlin,  British  Columbia.  It  is  stated, 
vaguely,  that  they  are  working  profitably,  but,  knowing  Atlin  as  I 
do,  I  am  skeptical.  This  same  frame  of  mind  clutches  me  when 
estimating  the  chances  of  dredging  in  all  the  northern  regions — 
Klondike,  Alaska,  Siberia.  The  climatic  factor  in  these  countries 
seems  to  me  almost  to  exclude  the  hope  of  profitable  results.  The 
short  season,  the  perennially  frozen  condition  of  much  of  the  ground, 
the  heavy  cost  of  labor,  and  the  great  distance  from  foundries  and 
sources  of  supply,  are  surely  drawbacks  of  almost  vital  importance. 
I  am  told  that  dredges  are  now  working  profitably  both  in  Klondike 
and  Alaska,  while  the  Russian  Minister  of  Mines  assured  me  that  a 
number  of  dredges  were  getting  payable  results  in  Siberia.  But  I 
am  still  skeptical.  I  have  never  seen  figures  or  results  from  any  of 
these  places.  I  shall  want  to  see  the  balance  sheets  for,  say,  two 
consecutive  years'  work  by  some  of  these  dredges,  before  I  can  be- 
lieve that  in  these  countries  the  climatic  factor  is  not  overpowering. 
South  America,  with  its  immense  river  systems,  offers  a  great 
field  for  possible  dredging  areas.  As  yet,  results  there  are  of  doubt- 
ful value.  Colombia  has  been  a  good  deal  prospected,  with,  I  be- 
lieve, not  satisfactory  results.  In  Dutch  and  French  Guiana  some 
dredges  are  working,  but  I  do  not  know  with  what  success.  I  lately 
read  a  report  on  ground  in  Peru,  stated  to  go  75c.  per  yd. 
The  writer  was  a  man  of  presumable  experience ;  had  he  not  been,  I 
should  have  looked  on  such  a  statement  as  a  fairy  tale.  This  ground 
lies  on  the  eastern  side  of  the  Andes,  and  a  dredge  would  have  to  be 
transported  in  sections.  Moreover,  as  for  a  long  distance  there  is 
a  precipitous  descent,  and  that  by  bridle-track  only,  the  sections  must 
be  no  heavier  than  a  couple  of  mules  could  carry  between  them.  It 
seems  to  me  that  a  dredge  thus  designed,  especially  if  working  in 
heavy  ground,  would  surely  be  a  failure.  I  should  like  information 
on  this  point — not  only  as  to  whether  it  can  be  sectionalized  down  to, 
say,  eight  cut  pieces — but  as  to  whether  it  can  be  expected  to  do 
satisfactory  work  on  that  basis.  Buenos  Ayres  has  recently  been 
the  scene  of  a  dredging  boom — on  paper.  The  locality  of  the  area 
thus  boomed  was  the  river  San  Juan  de  Oro,  in  Bolivia.  The  first 
dredge  started  there  worked  for  six  weeks  without  getting  as  much 
as  one  ounce  of  gold.  It  then  transpired. that  the  men  in  charge — 
picked  experts  of  reputation  from  New  Zealand — had  been  badly 
'salted'.  I  am  afraid  there  is  not  much  chance  for  success  in  this 
locality. 


186          DREDGING   FOR    GOLD   IN   CALIFORNIA. 

One  of  the  first  dredges  worked  in  South  America  was  located 
in  Matto  Grosso,  the  interior  province  of  Brazil.  This  dredge  has 
demonstrated  the  existence  of  gold  there ;  and  the  reports  of 
prospectors,  if  they  can  be  relied  upon,  point  to  a  large  area  of  pos- 
sibly payable  ground.  It  is  notable  that  the  Matto  Grosso  gravels 
carry  also  diamonds,  which  are  caught  on  the  dredge  in  considerable 
numbers.  Brains  are  now  at  work  devising  a  supplementary  plant, 
which  will  recover  the  diamonds  after  the  gravel  has  been  dredged 
for  its  gold.  Elsewhere  in  Brazil  there  is  a  good  deal  of  prospecting 
being  done,  but  in  a  manner  I  would  describe  as  superficial.  I  saw 
lately  a  dredge  at  work  in  the  river  near  the  old  mining  town  of 
St.  John  Del  Rey.  This  belonged  to  a  New  Zealand  company,  and, 
I  believe,  was  paying  expenses.  In  Tierra  del  Fuego  there  are  large 
areas  of  gravel  carrying  gold.  Those  on  the  Argentine  side  were 
extensively  prospected  by  two  friends  of  mine  last  season.  The  con- 
ditions were  pronounced  as  favorable,  but  there  was  too  little  gold 
present.  On  the  Chilean  side  there  are  some  undoubtedly  rich  areas ; 
but  here  the  ground  is  rougher,  and  would  require  a  specially 
adapted  type  of  dredge.  These  areas  may,  I  think,  be  reckoned  as 
possibilities. 

New  Zealand,  Victoria,  and  New  South  Wales,  alone  among 
Australasian  States,  seem  to  contain  payable  gold-dredging  areas — 
though  in  Tasmania  dredging  for  tin  is  now  being  done.  Even 
about  dredging  results  in  New  Zealand — the  home  of  the  industry — 
there  are  surprisingly  few  facts  available.  I  believe  that  one-third 
or  even  one-half  of  the  dredges  started  in  New  Zealand  have  worked 
at  a  loss ;  this  would  seem  to  indicate  that  the  methods  of  prospecting 
there  are  casual,  and  that  there  are  no  systematized  results  to  guide 
would-be  valuers  of  ground.  I  am  told  that  all  possible  dredging 
areas  in  New  Zealand  have  long  ago  been  secured,  also  that  at  the 
present  rate  of  exhaustion  most  of  the  best  ground  will  be  worked 
out  well  inside  12  or  15  years. 

After  numerous  failures,  especially  adapted  dredges,  or,  in 
cases,  hydraulic  pumps,  are  now  securing  fair  aggregate  results  in 
Victoria  and  New  South  Wales.  Most  of  the  areas  worked,  how- 
ever, are  of  small  extent,  and  profits  are  on  quite  a  small  scale.  As 
elsewhere,  it  seems  likely  that  the  areas  in  Australia  where  dredging 
conditons  are  favorable  will  prove  to  be  limited. 

In  Rhodesia,  or  rather  over  the  Rhodesian  border,  in  Mozam- 
bique, there  was  an  abortive  effort  at  dredging,  the  conditions  prov- 


APPENDIX.  187 

ing  unsuitable.  I  believe  this  is  the  only  dredge  erected  in  South 
Africa.  In  West  Africa  there  is  certainly  gold  in  the  rivers,  but  I 
am  skeptical  as  to  general  conditions.  There  are  some  half  dozen 
dredges  now  at  work  there,  but  their  results  are  indifferent ;  more- 
over, I  imagine  that  the  richest  patches  are  being  worked  first. 

As  regards  the  East,  there  is  not  much  yet  known  of  its  dredg- 
ing areas.  In  Burma,  on  the  Irrawaddy,  a  prospecting  dredge  has 
been  at  work  for  some  time.  I  understand  that  it  has  shown  profit- 
able figures,  but  I  have  no  facts  about  this.  However,  I  look  on 
Burma  as  among  the  possibilities.  It  seems  to  me,  also,  that  India 
is  a  country  to  be  prospected,  but  I  know  of  nothing  as  having  yet 
been  done  there.  Two  dredges  are  at  work  in  the  Malay  State  of 
Kelantau ;  from  the  published  returns  I  judge  that  they  are  not  pay- 
ing. In  Korea,  the  Oriental  Company  is  to  try  an  experiment  in 
dredging ;  while  it  is  stated  that  in  Borneo  and  the  Celebes  there  are 
hopeful  prospects. 

In  Europe,  there  are  several  dredges  at  work  in  Servia.  I 
believe  these  have  earned  a  commercial  profit,  for  others  are  being 
built ;  but,  as  usual,  there  are  no  precise  figures  available.  In  Hun- 
gary, there  might  be  dredging  areas,  but  I  suppose  the're  is  little  to 
be  expected  of  the  rest  of  Europe. 

As  I  started  out  to  ask  for  information,  not  to  give  it,  I  think 
I  have  said  all  that  is  compatible  with  my  premises,  and  I  shall  not 
venture  into  the  details  of  a  discussion  on  which  so  many  others 
must  be  better  informed.  I  can,  however,  say  first  this,  that  I  be- 
lieve the  Oroville  'school'  of  dredging,  both  in  methods  of  prospect- 
ing and  in  designing,  is  now  quite  ahead  of  New  Zealand,  and  that 
the  work  now  being  done  at  Oroville  and  Yuba  river  should  be 
studied  by  all  who  wish  to  master  the  details  of  this  subject.  The 
exact  results  from  the  Oroville  field  to  date,  together  with  the  de- 
scription of  the  prospecting  methods  employed  there,  and  an  account 
of  the  evolution  in  the  type  of  dredge  now  in  use  there,  written  by 
those  who  know,  would  form  a  valuable  nucleus  of  facts  on  which 
to  base  a  general  inquiry  into  the  whole  subject. 

J.  H.  CURLE. 

St.  Moritz,  Switzerland,  December  24,  1905. 


From   MINING   AND    SCIENTIFIC   PRESS,   January   27,    1906.,. 


188          DREDGING   FOR    GOLD   IN   CALIFORNIA. 


Gold  Dredging. 

The  comprehensive  glance  at  the  present  state  of  the  dredg- 
ing industry,  which  we  published  in  our  last  issue,  will  have  in- 
terested many  of  our  readers.  Few  men  have  such  acquaintance 
with  gold  mining  regions  as  the  author  of  'The  Gold  Mines  of 
the  World',  and  therefore  Mr.  Curie's  letter  commands  respect. 
It  was  a  useful  communication,  for  not  only  did  the  writer  of  it 
give  information,  but  he  fulfilled  the  equally  useful  function  of 
inciting  donations  of  knowledge  from  others.  Certainly  the 
knowledge  available  on  gold  dredging  is  amorphous  and  incom- 
plete ;  the  only  published  book  upon  it  is  rubbish,  because  it  was 
compiled  by  a  man  of  no  special  experience.  The  best  publica- 
tion on  the  subject  is  the  bulletin  issued  last  year  by  our  State 
Mining  Bureau.  Most  of  the  articles  heretofore  written  have 
been  too  vague,  too  little  anchored  to  facts  and  figures ;  a  few 
practical  contributions  emerge  out  of  this  mass  of  hazy  liter- 
ature and  these  have  been  prepared,  almost  without  exception, 
by  Western  engineers.  But  there  is  much  to  be  done  before  the 
gaps  in  our  information  on  this  important  branch  of  mining  are 
filled.  Mr.  Curie  specifies  the  several  points  concerning  which 
we  need  facts  and  figures,  and  we  are  confident  that  among  our 
readers  there  are  men  able  and  willing  to  contribute  what  is 
wanted.  Already  we  are  enabled  to  publish  a  special  article  on 
the  testing  of  dredging  ground,  with  a  workmanlike  description 
of  the  methods  to  be  used  in  checking  such  results. 

As  to  prospecting  ground  with  drills,  it  is  said  that  the  Oro- 
ville  experience  has  shown  a  yield  by  dredging  from  70  to  85  per 
cent  of  that  given  by  drilling  tests.  It  is  just  such  statements  as 
this  that  are  useless,  although  apparently  businesslike.  The 
value  of  a  series  of  drill-holes  as  indicating  the  richness  of  a  tract 
of  gravel  cannot  be  gauged  by  any  empirical  formula.  It  is  as 
absurd  as  the  practice  of  timid  engineers  who  cut  their  estimates 
of  ore  in  two  or  deduct  a  certain  fixed  percentage  from  their  cal- 
culations, so  as  to  be  safe.  In  the  case  of  drilling  before  dredg- 
ing, the  result  is  reliable  according  to  the  number  of  holes,  the 
distribution  of  them,  the  care  taken  in  the  work  and,  above  every- 
thing, the  personal  factor.  Such  work  carefully  done  and  checked 
at  each  stage  by  a  man  of  experience  and  integrity  needs  no  big 


APPENDIX.  189 

discounting,  while  that  accomplished  by  an  unreliable  driller  or 
a  careless  novice  is  worse  than  worthless.  No  fixed  percentage 
covers  the  varying  conditions  surrounding  an  engineering  opera- 
tion. 

In  the  early  days  of  dredging  it  was  the  custom  to  test  200 
acres  with  10  drill-holes;  nowadays  one  hole  to  two  acres  is  not 
uncommon.  When  results  indicate  that  the  gravel  is  of  varying 
,depth,  that  there  are  irregular  channels  or  that  the  ground  is 
spotty,  it  is  not  unusual  to  put  down  as  many  as  one  to  three 
holes  per  acre,  especially  where  no  adjoining  workings  exist, 
such  as  throw  light  on  any  anomalous  results  from  the  drilling. 
The  cost  is  a  limiting  factor,  for  each  hole  costs  $60  to  $100  in 
ground  of  any  considerable  depth. 

It  is  generally  assumed  that  the  results  given  by  shaft-sink- 
ing are  more  reHable  than  those  from  drill-holes ;  as  a  rule  this  is 
true,  but  the  comparison  too  often  smacks  of  the  old  idea  that  a 
mill-run  is  more  trustworthy  than  the  sampling  of  ore  in  a  mine. 
It  depends  upon  how  it  is  done,  with  this  proviso,  that  the  more 
men  needed  to  carry  out  an  operation  of  sampling,  the  greater 
the  opportunity  for  error,  intentional  or  unintentional.  A  shaft 
gives  better  opportunity  for  examining  the  nature  of  the  succes- 
sive layers  of  gravel  and  other  conditions  that  bear  upon  the  sub- 
sequent working  of  the  ground.  Careful  measurements  are  im- 
perative ;  sometimes  it  is  not  practicable  to  hold  the  same  diam- 
eter of  shaft  all  the  way  down,  and  in  running  ground  one  has  to 
resort  to  timbering;  these  factors  affect  the  cross-sectional  area 
and  must  be  carefully  noted  in  any  calculations.  Moreover,  in- 
stances are  known  where  shaft  results  have  been  seriously 
vitiated  by  the  fact  that  the  particles  of  gold  have  fallen  to  the 
bottom,  with  the  water,  so  that  the  upper  layers  of  gravel  ap- 
peared worthless,  while  that  immediately  above  bedrock  was 
excessively  enriched.  Great  caution,  bred  of  experience,  is  re- 
quired to  make  an  accurate  test. 


Editorial   MINING  AND  SCIENTIFIC  PRESS,   February   3,    1906. 


190         DREDGING   FOR   GOLD   IN   CALIFORNIA. 


Sectional  Dredging  Machinery. 

In  our  last  issue,  we  endeavored  to  stimulate  a  discussion 
on  gold  dredging  by  referring  to  the  methods  employed  in  test- 
ing ground  by  drilling.  This  week  we  publish  the  continuation 
of  an  article  on  this  subject.  Another  important  point  in  con- 
nection with  dredging  is  the  degree  to  which  it  is  safe  to  sec- 


Fig.  102.     Wreck  of  the  Colorado-Pacific,  one  of  Earliest 
Boats  Built  at  Folsom. 

tionalize'the  heavy  parts  of  a  dredge.  It  is  obvious  that  such 
subdivision  must  be  a  last  resort.  To  sectionalize  dredging 
machinery,  the  chief  essential  of  which  is  strength,  is  like  dividing 
a  stamp-mill  mortar  where  solidity  is  the  first  requisite.  The  ordi- 
nary dredge  equipped  with  5-ft.  buckets  employs  a  shaft  and  tumbler 
weighing  together  about  six  tons ;  the  shaft,  made  of  nickel  steel,  is 
14  inches  in  diameter  and  is  8^2  feet  long,  so  that  it  weighs  over  a 
ton — usually  about  2500  pounds.  Each  bucket-base  weighs  1100 
pounds,  and  even  the  pins  are  over  a  hundred  pounds  apiece.  Ob- 
viously, to  cut  down  the  parts  of  such  machinery  to  the  250  or  350 


APPENDIX.  191 

pounds  that  a  mule  can  carry,  is  a  difficult  matter.  The  tendency  in 
California  is  to  attain  efficiency  and  economy  by  building  the  dredges 
enormously  strong  and  big.  There  is  a  dredge  at  Folsom — treating 
150,000  cubic  yards  per  month — that  has  close-connected  buckets  of 
13-ft.  capacity,  and  another  13-ft.  dredge,  but  of  the  intermediate  or 
linked  bucket  type,  designed  by  Julius  Baier,  has  been  erected  in 
Montana.  Dredges  such  as  these  are  beyond  the  transporting 
capacity  of  all  the  mules  in  creation.  The  ordinary  and,  as  regarded 
nowadays,  small  machine  with  3-ft.  close-connected  buckets  is  pro- 
vided with  an  8-inch  shaft  weighing  1155  pounds  and  uses  a  bucket- 
base  of  475  pounds.  Even  such  a  dredge  could  not  be  transported 
over  mountainous  country.  To  decrease  the  burden,  the  shaft  could 
be  worked  into  the  tumbler  casting,  so  that  the  weight  would  be 
distributed  into  thirds.  The  bucket-base  is  difficult  to  reduce,  save 
by  cutting  in  half,  at  big  expense.  This  applies  to  the  close-con- 
nected type ;  for  a  bucket  and  link  dredge  of  3-ft.  capacity,  a  six-inch 
shaft  would  suffice  and  the  weight  would  be  one-half  that  given 
above.  By  using  a  built-up  bucket-base  instead  of  a  solid  steel  cast- 
ing each  piece  can  be  reduced  to  150  pounds;  with  sacrifice  of 
strength,  of  course.  Such  construction  will  require  a  pneumatic 
riveting  machine  for  assembling  the  parts.  However,  these  are  de- 
tails beyond  our  province.  We  desire  merely  to  stimulate  intelli- 
gent discussion  on  the  subject  and  we  trust  our  professional  friends 
will  avail  themselves  of  the  opportunity. 


Editorial   MINING   AND   SCIENTIFIC   PRESS,    February    10,    1906. 


192          DREDGING   FOR    GOLD   IN   CALIFORNIA. 

Sectional  Dredging  Machinery. 

The  Editor : 

Sir — As  regards  sectionalizing  placer  dredging  machinery  for 
use  in  remote  regions ;  it  is  obvious  that  the  boilers,  engines,  and 
such  parts  as  have  been  sectionalized  for  other  purposes  may  be 
readily  obtained  in  shape  for  mule-back  transportation.  There  are, 
however,  various  portions  of  the  machine  which  it  seems  at  present 
could  not  be  sectionalized  satisfactorily  to  the  required  weight  or 
size  of  piece  which  may  be  transported  in  this  manner. 

The  standard  type  of  dredge  used  in  California  uses  a  bucket 
having  a  capacity  of  5  cu.  ft. ;  it  has  a  cast-steel  back  weighing  from 
850  to  1000  Ib.  Bucket-backs  of  lighter  weight  have  been  discarded 
in  favor  of  the  heavier,  on  account  of  the  increased  wear  obtainable. 
It  is  true  that  a  built-up  bucket  either  of  the  continuous  or  open- 
link  type  can  be  built  of  small  pieces  riveted  together,  but  actual 
practice  demonstrates  that  the  solid  cast-steel  back  is  preferable  in 
every  respect.  It  is  true  we  are  using  in  California  some  dredges 
with  3-cu.  ft.  buckets,  those  of  the  open-link  type  with  built-up 
buckets  having  an  actual  capacity  of  from  600  to  750  cu.  yd.  per 
day,  while  the  continuous-bucket  type  with  cast-steel  bucket-back 
will  average  from  1000  to  1500  cu.  yd.  per  day,  in  the  average 
digging,  without  trouble.  The  upper  tumbler  for  driving  the  bucket- 
chain  it  would  be  practically  impossible  to  sectionalize ;  in  fact,  the 
latest  practice  in  this  respect  calls  for  a  six-sided  tumbler,  in  place 
of  the  old  five-sided,  not  because  six  sides  are  better  for  driving  or 
for  the  dumping  of  the  bucket,  the  fact  being  to  the  contrary,  but 
because  practice  has  established  a  size  of  shaft  which  it  is  practically 
impossible  to  pass  through  the  old  type  of  five-sided  tumbler.  The 
shafts  are  getting  heavier  annually.  From  my  personal  experience, 
dating  back  to  1893,  I  can  say,  that  at  that  time  we  considered  a  6^2 
to  7-in.  shaft  as  ample  for  driving  a  5-cu.  ft.  bucket-chain  into  the 
tightest  of  soil.  Recent  construction  calls  for  hollow-forged  and 
oil-tempered  nickel-steel  shafts,  the  very  finest  that  can  be  produced, 
of  a  diameter  ranging  from  \\y2  to  14  in.;  and  as  these  shafts  are 
•from  8  to  10  ft.  long,  according  to  the  type  of  drive  used,  the  piece 
is  necessarily  very  heavy,  and  there  seems  to  be  no  possible  way  to 
reduce  its  weight  for  packing  over  a  mountain  trail.  In  fact,  one 
five-foot  dredge,  to  my  knowledge,  was  fitted  with  a  hollow-steel 


APPENDIX.  193 

shaft  18^/2  in.  diam.,  and  approximately  11  ft.  long,  which  it  would 
have  been  impossible  to  have  made  in  more  than  one  piece.  Other 
various  portions  of  the  dredge  could  probably  be  sectionalized  to 
quite  an  extent,  and  in  the  case  of  remote  operations  a  dredge  could 
undoubtedly  be  built  which  would  handle  a  reasonable  quantity  of 
gravel  and  not  have  any  parts  too  heavy  for  mule-back  transporta- 
tion. A  dredge  which  closely  approximates  the  necessary  condi- 
tions for  this  purpose  was  built  by  Mr.  Ogilvie,  of  Dawson,  from 
designs  of  A.  Wells  Robinson,  of  Montreal,  and  was  put  in  operation 
on  the  Stewart  river.  Buckets  were  of  2^4  cu.  ft.  on  alternate  links 
of  the  chain,  and  the  dredge  was  intended  for  excavation  not  to 
exceed  15  ft.  below  water-line.  The  dredge  has  been  successfully 
used  in  prospecting  various  portions  of  the  Stewart  river,  and  now 
lies  on  the  Yukon  a  short  distance  below  Dawson.  It  will  probably 
be  used  next  season  for  prospecting  other  parts.  The  fact  still  re- 
mains, however,  that  if  one  has  sufficient  acreage  of  placer  ground 
which  is  suitable  for  dredging  purposes,  and  which  is  remote  from 
the  common  carriers,  if  the  ground  is  sufficiently  rich  to  warrant  his 
dredging  it  for  a  profit,  the  cost  of  constructing  a  road  which  would 
permit  his  machinery  to  be  hauled  to  the  ground  in  the  usual  form 
would  be  so  small  in  proportion  to  the  profits  on  the  operation  that 
distance  from  transportation  need  not  deter  anyone  from  entering 
into  the  dredge  business.  I  have  certain  knowledge  of  machines  of 
the  usual  type  which  have  been  hauled  over  mountain  trails  70  to 
150  miles  from  a  railroad  station,  and  in  cases  where  the  owner  was 
obliged  to  make  the  road  or  trail  over  which  the  machinery  was 
hauled,  and  in  one  case  even  to  send  to  the  Eastern  States  for 
wagons,  harness,  etc.,  and  to  Kansas  for  mules,  in  order  to  get  his 
machinery  on  the  ground,  and  the  dredge  has  repaid  its  entire  cost 
of  installation,  and  all  expenses  connected  with  purchasing  the 
ground,  prospecting  it,  and  maintaining  it,  and  a  profit  -besides  of 
over  150%  on  the  total  capitalization  of  the  venture,  although  it  has 
only  been  in  operation  three  years.  The  prospecting  shows  an 
average  value  of  16c.  per  cubic  yard.  This  dredge  is  driven  by 
steam  and  burns  the  poorest  quality  of  spruce  wood  for  fuel  at  a 
cost  of  nearly  $4  per  cord  at  the  dredge,  and  the  dredge  consumes 
15  cords  per  day. 

G.  L.  HOLMES. 
San  Francisco,  February  8,  1906. 

From  MINING  AND  SCIENTIFIC  PRESS,  February   17,   1906. 


194          DREDGING   FOR   GOLD   IN   CALIFORNIA. 

Gold  Dredging. 

The  Editor: 

Sir — Mr.  Curie's  criticism,  in  .the  issue  of  January  27,  1906,  of 
the  dredging  industry  is  timely,  and  worthy  of  the  attention  which 
he  evidently  wishes  it  to  receive.  I  will  give  a  little  consideration  to 
some  of  his  points,  with  reference  to  the  Alaska  field,  and  other 
regions. 

In  order  to  consider  this  question:  Divide,  mentally,  Alaska 
into  three  provinces,  (a)  South  Coast  province,  (b)  Interior  prov- 
ince, (c)  Seward  Peninsula  province.  Now  eliminate  all  per- 
manently frozen  ground.  This  consideration  strikes  out  at  once 
almost  all  of  the  Seward  Peninsula,  including  the  region  about 
Nome,  and  all  north  of  Nome  to  the  west  of  the  treeless  area.  It 
also  bars  the  whole  of  the  Interior  province,  with  the  possible  ex- 
ception of  extraordinarily  rich  creek-beds,  like  Bonanza  creek  on 
the  Klondike,  where  the  material  has  been  already  loosened  and  dis- 
turbed by  previous  work,  and  portions  of  the  Klondike  river-bed. 
The  South  Coast  province  only  remains.  I  would,  therefore,  elim- 
inate from  consideration  as  dredging  ground  at  least  four-fifths  of 
the  Territory  of  Alaska. 

By  the  South  Coast  province  I  mean  the  strip  extending  from 
the  southern  boundary,  along  the  coast,  north  and  west ;  this  includes 
the  high  frontal  ranges  of  mountains  of  the  Alexander  archipelago, 
the  St.  Elias  and  Yakutat  districts,  Kodiak  island,  the  Kenai  and 
Alaska  peninsulas,  the  Aleutian  islands,  and  the  area  lying  between 
the  north  shore  of  Bristol  bay  and  the  Kuskokwim  river.  In  the 
areas  mentioned  permanently  frozen  gravel  does  not  occur. 

All  the  territory  lying  east  of  the  149th  meridian  may,  I  think, 
be  eliminated.  Flood  plains  reduced  nearly  to  base  level,  in  which 
streams  meander,  are  in  my  opinion  the  first  requisite  for  auriferous 
gravels  fit  for  dredging.  Unless  this  prime  geological  feature  is 
present,  it  is  not  likely  that  suitable  ground  exists,  and  the  engineer 
wastes  his  time  and  that  of  his  client  in  examining  the  area.  As  I 
do  not  own  dredges,  and  further  as  I  do  not  have  cognizance  of  any 
balance  sheets  except  those  of  the  California  companies,  it  is  im- 
possible for  me  to  answer  some  of  Mr.  Curie's  inquiries.  I  believe, 
however,  that  in  Alaska  there  has  been  no  successful  operation  up 
to  the  present  time  in  the  South  Coast  province.  It  is  reported  that 


APPENDIX.  195 

a  dredge  built  on  the  Solomon  river,  Seward  Peninsula,  which  has 
operated  during  the  season  of  1905-6,  has  been  successful.  We  have 
no  published  statement  about  it  up  to  the  present,  however.  Grant- 
ing the  success  of  this  dredge,  it  is  due  to  exceptional,  very  excep- 
tional, conditions  in  that  district  and  latitude,  a  repetition  of  which 
one  may  not  expect  to  encounter.  I  therefore  unhesitatingly  con- 
demn the  Seward  Peninsula  as  a  dredging  province.  By  this  I  do 
not  wish  to  say  that  rich  placers  do  not  occur  there.  The  gold  is 
there,  but  among  the  methods  of  working,  dredging  is  not  to  be 
considered. 

The  portion  of  the  South  Coast  province  which  appears  most 
promising  for  dredging  lies  to  the  west  of  Cook  inlet,  the  Sushitna 
river  and  to  the  south  of  Bristol  bay.  The  tributaries  of  the  Yentna 
river,  which  is  itself  a  tributary  of  the  Sushitna,  should  be  investi- 
gated! Outside  of  the  area  above  named,  I  know  of  no  Alaska  area 
which  is  worth  the  dredge-investor's  prospective  consideration.  Mr. 
Curie  asks :  How  many  payable  dredging  areas  are  known  in  the 
world?  I  should  say  portions  of  California,  including  the  Feather 
and  Yuba  river  areas,  and  parts  of  New  Zealand.  As  regards  prob- 
able areas,  I  may  be  permitted  to  suggest  eastern  Russia.  I  wit- 
nessed dredge  construction  there  in  1902.  I  have  heard  that  several 
dredges  have  since  been  constructed.  The  factor  of  climate,  to 
which  Mr.  Curie  refers,  needs  some  definition.  If  he  refers  to  per- 
manent frost  in  the  gravel,  I  am  in  entire  agreement  with  him,  and 
would  offer  the  same  objections  to  the  Olekma,  Vitim,  and  Amgoon 
districts  as  to  the  Nome  district.  If,  on  the  other  hand,  he  refers  to 
the  disadvantage  of  short  working  season  to  which  northern  areas 
are  subject,  I  do  not  think  his  objections  altogether  valid,  as  I  believe 
the  Ural  offers  an  extensive  and  promising  field  for  exploration. 

The  Atlin  district  is,  I  will  admit,  an  extremely  hazardous 
locality  for  dredging.  The  gravel  is  not  particularly  rich.  By  this 
I  mean  that  the  ancient  benches,  if  worked  as  a  whole  (and  there  is 
no  other  auriferous  alluvium  .to  be  considered  there),  will  not  run 
over  20c.  per  cu.  yd.  The  wash  is  extremely  heavy,  and  the  thick- 
ness is  above  90  ft.  except  in  very  limited  areas.  The  season  does 
not  exceed  150  days,  and  even  this  is  long  for  that  region.  For  the 
matter  of  gold  and  its  profitable  exploitation  by  some  form,  Atlin  is 
not  without  possibilities,  but  the  method  will  have  to  be  some  other 
than  dredging. 


196          DREDGING   FOR    GOLD   IN   CALIFORNIA. 

Dredging  in  South  America  is  a  fact,  but  the  conditions  of  ac- 
cess to  most  of  these  regions  have  hitherto  been  prohibitive,  and  it 
may  be  said  that  dredging  capital  will  turn  its  attention  to  many 
other  parts  of  the  world  before  hazarding  investment  in  South 
America.  Recently  we  have  heard  of  a  gold  and  diamond  dredging 
field  in  the  vicinity  of  Diamantina,  Brazil.  The  ground  is  now  being 
explored  and  I  understand  the  gravel  is  being  drilled.  It  is  possible 
there  is  a  profitable  field  for  dredging  investment  in  this  isolated 
region,  but  it  will  be  some  time  before  results  can  be  given  to  the 
mining  public. 

Mr.  Curie  says  that  probably  one-third,  or  even  one-half,  the 
dredges  started  in  New  Zealand  have  worked  at  a  loss.  This  fact  is 
not  a  condemnation  of  a  dredging  province.  In  California,  outside 
the  comparatively  small  area  about  Oroville,  Marysville,  and  Folsom, 
there  are  many  so-called  dredging  districts,  but  the  investigator 
finds  that  the  word  dredge  is  much  more  common  than  the  word 
dividend. 

In  the  United  States  proper,  with  the  exception  of  the  opera- 
tions already  noted  in  California,  the  public  knows  of  no  profitable 
gold  dredging,  from  authenticated  published  statements,  although  in 
Montana,  Idaho,  Arizona,  and  Colorado  dredging  operations  have 
been  attempted,  and  there  are  rumors  that  some  dredges  have  been 
made  to  pay.  Georgia  has  furnished  one  small  patch  of  dredging 
ground  which  I  believe  was  payable,  namely,  that  of  the  Chestatee 
river,  below  Dahlonega.  I  do  not  think  it  impossible  that  limited 
portions  of  river  beds  in  auriferous  areas  of  North  and  South  Caro- 
lina and  Georgia  may  yet  be  profitably  dredged.  It  is  highly  prob- 
able that  in  Burma  and  British  India  dredging  fields  will  yet  be 
found.  The  peculiar  conditions  of  weathering  which  exist  there  in 
the  auriferous  belts  should  afford  the  proper  conditions  for  soft 
bedrock,  and  the  portions  of  the  river  flood-plains,  lying  midway 
between  the  sources  and  the  sea,  should  be  prospected. 

In  regard  to  the  amount  of  gold  which  is  produced  yearly  by 
dredges,  Mr.  Aubury  has  told  us  from  reliable  data  how  much  is 
produced  in  California,  and  I  believe  this  represents  nearly  the  whole 
product  of  the  United  States.  The  amount  produced  in  New  Zea- 
land I  have  no  means  at  present  of  knowing ;  the  amount  produced  in 
other  parts  of  the  world  is  at  present  insignificant.  The  estimate  of 
future  production  in  California  is  conservatively  $200,000,000,  as 
may  be  deduced  from  Mr.  Aubury's  figures. 


APPENDIX.  197 

I  should  say  that  the  number  of  dredges  in  all  parts  of  the  world 
which  are  working  at  a  profit  does  not  exceed  one  hundred.  Of  the 
number  of  dredges  which  were  once  worked  and  are  now  not  work- 
ing, one  can  form  only  the  roughest  estimate.  If  one  hundred  are 
working  at  a  profit,  it  is  safe  to  say  there  are  five  times  this  number 
idle  or  abandoned.  Although  this  seems  a  large  penalty  to  pay  for 
experimental  work,  if  the  expenditure  eventually  results  in  the  e^tab- 
lishment  of  a  sound  producing  business  in  various  parts  of  the  world, 
it  will  not  be  considered  excessive. 

The  precise  costs  of  dredging  in  various  localities  are  probably 
known  to  Mr.  Curie  as  well  as  to  anyone.  Eight  cents  at  Oroville, 
80c.  in  the  Klondike,  and  50c.  per  cu.  yd.  in  the  Seward  Peninsula  of 
Alaska,  are  the  figures  of  which  I  feel  fairly  sure.  The  high  cost  in 
the  Klondike  is  where  gravel  is  thawed  by  steam-points  in  front  of 
the  dredge  as  it  progresses.  The  Alaska  figure  assumes  a  season  of 
120  days,  and  delays  are  occasioned  by  annual,  but  not  permanent, 
frost.  New  Zealand  costs  are  said  to  be  very  low,  but  I  have  no 
figures  at  hand. 

Regarding  costs  in  the  Ural  region,  which  I  have  indicated  as 
the  best  field  in  the  Russian  empire,  all  conditions  considered,  I 
would  allow  an  average  season  of  180  days.  The  cost  on  this  basis, 
assuming  a  ten-year  life,  not  to  exceed  $500  per  acre  for  the  ground 
as  purchased,  $75,000  each  for  the  dredge  installations  with  a  capac- 
ity of  1500  cu.  yd.  per  day,  in  30- ft.  average  ground,  is  14c.  per  cu. 
yd.  This  is  taking  the  highest  figure  for  operating  at  Oroville  and 
adding  to  it  depreciation,  amortization,  and  interest  on  total  in- 
vested capital,  making  an  extra  charge  of  six  cents  per  cubic  yard. 

In  general,  the  cost  of  dredging  is  not  seriously  affected  by 
nature  of  deposit  for  the  reason  that  dredging  in  deep  ground,  for 
example  60  ft.,  merely  increases  the  first  cost  of  installation  and  does 
not  seriously  affect  the  operating  cost.  Ground  containing  numer- 
ous and  large  boulders  cannot  be  dredged  at  all,  so  this  kind  of  de- 
posit need  not  be  considered.  Likewise  ground  with  too  great  an 
overburden  of  turf  or  muck  cannot  be  profitably  dredged.  Likewise 
ground  which  is  too  shallow  cannot  be  dredged,  but  should  be 
worked  by  steam-scrapers.  By  elimination  of  the  objectionable  types 
of  ground,  it  will  be  found  that  the  cost  of  working  real  dredging 
ground  will  not  greatly  vary  in  California,  Burma,  or  European 
Russia.  If  anything,  the  operating  cost  will  be  somewhat  greater  in 
the  two  latter  countries.  As  regards  power,  where  dredges  are 


198         DREDGING   FOR   GOLD   IN   CALIFORNIA. 

operated,  as  at  Oroville,  by  a  general  power-system,  the  cost  will  be 
less  than  for  self-contained  dredges  operated  by  steam,  unless  fuel  is 
remarkably  cheap. 

Prospecting  of  dredging  ground  should  be  done  by  pit-sinking 
if  possible;  as  this  method  is  rarely  feasible,  drilling  with  churn- 
drills  is  generally  requisite.  This  subject  has  been  so  thoroughly 
discussed  recently  that  I  shall  leave  it  to  those  best  qualified  to 
answer.  For  the  determination  of  the  proper  factor  to  apply  in  each 
case  of  an  examination,  I  unhesitatingly  recommend  the  sinking  of 
a  pit  around  the  drill-hole  if  possible,  in  at  least  ten  per  cent  of  the 
number  of  holes  drilled,  to  check  the  drilling  results. 

The  proper  valuation  of  dredging  ground  should  be  made  on  a 
system  which  eliminates  all  doubtful  territory  from  consideration. 
For  example,  in  a  base-level  valley  suitable  for  dredging  there  may 
be  an  average  width  of  1500  ft.  of  gravel-flat  covered  by  marsh, 
forest,  underbrush ;  in  any  of  which  an  open-cut  to  accommodate  the 
dredge-hull  may  be  dug.  There  may  be  a  meandering  stream  four 
or  five  feet  deep,  which  is  subject  to  spring  freshets  occupying  500 
ft.  of  a  given  cross-section  of  the  valley.  The  danger  of  working 
in  this  stream  should  be  taken  into  consideration,  as  the  dredge  may 
be  wrecked  by  a  flood,  if  operations  are  attempted  in  the  present 
water-course.  Let  us  say  that  all  the  area  outside  the  limits  of  the 
river  is  workable.  But  at  best,  only  a  small  area  near  either  bank  in 
the  river  itself  is  dredgeable,  and  it  is  a  risk  to  allow  for  the  gold 
which  may  underlie  the  main  body  of  the  present  stream.  To  this  it 
may  be  objected  that  in  certain  dredging  areas  the  auriferous  channel 
is  coincident  with  the  course  of  the  present  river.  I  reply  that  an 
area  presenting  such  geological  conditions  is  not  in  a  bona  fide  dredg- 
ing province,  as  it  does  not  represent  dredging  ground  founded  on 
the  Oroville  province  as  a  type ;  namely,  where  the  gold  is  fine  and 
distributed  with  a  fair  amount  of  uniformity  over  a  wide  compara- 
tively shallow  area. 

In  further  considering  the  valuation  of  dredging  ground,  I 
would  urge  the  suggestion  that  while  operating  expenses  have  been 
published  in  considerable  detail,  the  valuer  of  dredging  ground  has 
few  data  concerning  the  cost  of  ground  and  equipment.  If  operat- 
ing expenses  at  Oroville,  for  example,  are  being  reduced  to  five  cents 
per  cubic  yard  and  under,  what  additional  cost  per  cubic  yard  must 
be  figured  for  the  annual  consumption  of  the  ground,  and  to  allow 
for  the  amortization  of  the  machinery?  Scrap  iron  is  no  great  asset, 


APPENDIX.  199 

and  that  is  all  a  dredge  amounts  to  after  the  gold  which  it  is  winning 
for  its  owner  is  removed. 

I  think  it  must  be  confessed  to  inquirers  like  Mr.  Curie,  that  the 
proper  system  of  valuing  ground  on  such  a  basis  as  to  show  the 
probable  net  proceeds  of  the  operation,  has  not  been  discovered.  At 
least  I  have  never  seen  published  a  balance  sheet  of  a  gold-dredge 
which  shows  how  much  it  earns  over  all  expenses.  Oroville  has 
given  us  the  data  for  estimating  actual  as  against  theoretical  work 
in  cubic  yards  handled.  The  present  excessive  cost  of,  and  time  con- 
sumed in,  repairs  will  probably  be  reduced,  but  Oroville  experience 
gives  us  the  best  basis  for  estimating,  as  yet.  The  life  of  the  prop- 
erty can  be  determined  by  prospecting,  and  the  yardage  and  cost  of 
each  dredge  being  a  fairly  well-determined  factor,  operating  cost 
being  estimated  from  local  conditions,  the  eventual  net  proceeds 
ought  to  be  foretold  with  a  fair  degree  of  accuracy.  No  valuation 
of  dredging  ground  which  does  not  thus  allow  for  amortization  of 
the  total  preliminary  expense  of  acquiring,  prospecting,  and  equip- 
ping, in  addition  to  fixed  charges  for  operating  for  a  given  length  of 
time,  appears  to  me  worthy  of  consideration. 

C.  W.   PURINGTON. 

Denver,  July  15,  1906. 


From  MINING  AND  SCIENTIFIC  PRESS,  July  28,   1906. 


200          DREDGING   FOR    GOLD   IN   CALIFORNIA. 

Gold  Dredging. 

The  Editor: 

Sir — In  the  issue  of  your  paper  of  January  27,  1906,  under 
the  heading  of  'Gold  Dredging,'  J.  H.  Curie  asks  seven  specific 
questions,  and  the  article  goes  on  to  give  a  great  deal  of  valuable 
information  which,  on  two  points,  I  venture  to  think,  is  a  little 
misleading.  In  referring  to  the  Yuba  district,  Mr.  Curie  states 
that  a  large  area  of  gravel  90  ft.  deep  gives  good  returns,  and 
that  the  dredges  there  are  to  work  to  that  depth.  Though  the 
drilling  in  the  Yuba  field  discloses  the  fact  that  gold  values  are 
contained  at  least  to  a  depth  of  115  ft.,  it  has  only  been  considered 
advisable  to  build  boats  fitted  to  dig  at  their  greatest  advantage 
to  depths  not  over  70  feet. 

This  article  was  published  in  January,  1906,  and  at  the  pre- 
sent date  there  are  ten  dredges  at  work.  All  of  these  are  equipped 
to  dig  to  64  ft.  below  water  line,  and  the  deepest  work  that  is, 
or  has  been,  done  there  is  at  a  depth  of  72  ft.  below  water  line. 
Under  the  conditions  prevailing  on  the  Yuba  the  water  line  is, 
as  a  rule,  only  a  few  feet  below  the  actual  surface — in  some  cases, 
indeed,  the  dredging  ponds  have  to  be  kept  pumped  out  so  that 
the  surface  of  the  dredging  ground  may  be  above  water  and  in 
order  that  the  digging  ladder  may  reach  the  depth  mentioned. 
This,  so  far  as  I  am  aware,  is  the  greatest  depth  to  which  dredging 
has  been  carried  in  any  part  of  the  world,  but  as  the  best  values 
in  dredging  lands  in  the  majority  of  cases  lie  close  to  the  bottom 
of  the  digging  it  is  not  hard  to  see  that  an  overburden,  if  com- 
mercially unproductive,  simply  tends  to  reduce  the  profit — or,  in 
other  words,  to  lower  the  average  grade  per  yard  of  the  material 
which  it  is  necessary  to  handle. 

The  other  point  to  which  exception  may  be  taken  is  contained 
in  the  concluding  sentences  where  it  is  inferred  that  Oroville 
and  Yuba  districts  should  be  studied  as  the  most  modern 
examples  of  up-to-date  prospecting,  designing,  and  dredging.  The 
name  of  Folsom  is  only  conspicuous  by  its  absence.  In  my 
humble  opinion  this  district  should  rank  at  least  with  the  others 
for  all  and  more  of  the  qualifications  mentioned.  It  is  not  only 
the  most  important  as  having  the  largest  available  area  of  dredg- 


APPENDIX.  201 

ing  ground;  but  (in  some  cases  under  unique  conditions)  illus- 
trates the  handling  of  the  largest  yardage  per  boat  of  any  locality 
in  the  world,  and — as  far  as  can  be  learned — at  as  low  an  average 
cost  per  yard. 

I  have  recently  completed  an  extensive  examination  of  the 
dredging  fields  of  Oroville,  Yuba,  and  Folsom  in  the  Sacramento 
valley,  and  have  investigated  fully  most  of  the  points  embodied 
in  Mr.  Curie's  seven  specific  questions.  Those  questions  were : 

1.  How   many   payable   or   probably   payable   dredging   areas 
are  known  in  the  world,   and  what  is  approximately  their   gross 
extent?     Which  are  the  likeliest  countries  to  prospect? 

2.  How  much  gold  is  produced  yearly  by  dredges  and  how 
much  of  the  production  is  profit? 

3.  How  many  dredges  are  now  working  at  a  profit? 

4.  How  many  dredges  that  were  once  worked  are  not  now 
worked,  and  what  were  the  reasons  for  their  stoppage  ?    How  much 
money  do  these  represent? 

5.  What  are  the  precise  costs  in  different  localities?      How 
are  costs  affected  by:      a.    Type  of  dredge;  \b.  nature  of  deposit; 
c.  nature  of  power,  and  d.  climate? 

6.  What  is  the  best  system  of  prospecting  dredging  ground? 
How  should  such  system  be  adapted  to  different  kinds  of  ground? 
Is  drilling  as  effective  as  sinking  shafts  or  paddocks?      What  is 
the  average  recovery  of  the  gold  contents  as  shown  in  prospecting? 
Why  are  favorable  results  in  prospecting  often  falsified  in  practice? 

7.  Assuming  prospected  or  otherwise  proved  ground  to  repre- 
sent 'ore  blocked  out,'  which  is  the  correct  basis  of  valuation  for 
such  ground? 

As  the  results  of  my  investigations  are  shortly  to  appear  in 
print,  I  shall  simply  refer  to  Mr.  Curie's  queries  in  a  brief  man- 
ner. 

No.  1  does  not  apply  to  this  locality. 

No.  2.  This  is  a  difficult  question  to  answer  accurately  in 
detail,  because  the  information  is  not  fully  obtainable.  However, 
assuming  that  at  Oroville,  the  average  total  working  cost  is 
7c.  per  yd.,  the  average  recoverable  value  of  the  gravel  14c., 
and  the  annual  yardage  produced  about  19,200,000;  then  there 
is  a  total  annual  production  of  $2,688,000,  of  which  $1,344,000 
is  net  profit.  On  the  Yuba  the  annual  yardage  is  from  9,600,000 


202 


DREDGING   FOR   GOLD   IN   CALIFORNIA. 


to  10,200,000.  The  recoverable  value  of  the  gravel  has  been  esti- 
mated at  20c.  per  yd.,  then  assuming  that  the  working  cost  is 
5.5c  per  yd.,  the  total  annual  production  is  $2,000,000,  and  the 
profit  $1,450,000. 

At  Folsoin  figures  of  this  sort  are  difficult  to  obtain,  but  the 
average  value  over  the  whole  tract  is  probably  not  over  lie., 
though  in  places  it  will  run  much  higher  than  this  figure.  Taking 
the  average  working  cost  as  5c.  per  cu.  yd.,  and  the  total  annual 
product  as  8,500,000  cu.  yd.,  the  profit  is  estimated  at  $510,000. 

Therefore  in  the  three  districts  an  approximate  estimate  of 
the  total  annual  production,  the  average  recovery  per  yard,  the 
average  cost  of  working  per  yard,  and  the  total  annual  net  profit 
may  be  summarily  expressed  in  tabular  form  as  follows : 


District 

Annual  opera- 
tions in  cu.  yd. 

Production 

Recovery  per 
cu.  yd.  in  cents 

Cost  percu.  yd. 
in  cents 

Annual  profit 

Oroville  .... 
Yuba  
Folsom   .... 

19,200,000 
9,600,000 
8,500,000 

$2,688,000 
2,000,000 
935,000 

14 

20 

11 

7 
5.5 
5 

$1,344,000 
1,450,000 
510,000 

Total   

37  300  000 

$5  623  000 

$3  304,000 

No.  3.  In  the  three  districts  there  are  forty-nine  dredges  in 
operation,  of  which,  say  forty-one  have  been  working  over  nine 
months.  Of  the  latter  number  probably  over  90%  are  working  at  a 
profit,  while  undoubtedly  all  of  the  remaining  eight  will  pay  divi- 
dends. 

No.  4.  Only  two  dredges  that  are  not  now  working  are  still 
fit  for  operation,  all  the  others  having,  through  service,  become 
mechanically  unfit  for  use.  Of  these  two,  one  is  of  too  small 
capacity  and  is  practically  worn  out,  while  the  other  is  also  of 
ancient  design,  but  could  be  remodeled  and  used.  After  litigation 
it  was  sold  at  sheriff's  sale.  The  property  on  which  it  operated 
is  still  commercially  valuable  from  a  dredging  point  of  view.  The 
two  dredges  probably  originally  represented  about  $95,000. 

No.  5.  The  costs  have  been  given  in  the  answer  to  question 
No.  2. 

a.  The  type  of  dredge  affects  the  cost  of  production  chiefly 
as  regards  its  digging  capacity,  this  being  favorable  in  proportion 
to  the  increase  in  size  of  buckets  up  to  at  least  7l/2  cu.  ft.,  and 
probably  up  to  13  cu.  ft.,  where  proper  repair  facilities  are  avail- 


APPENDIX.  203 

able  and  several  machines  are  operated  under  one  management. 
Fixed  costs  are  reduced  in  the  larger  machines  and  output  is 
increased. 

b.  The  nature  of  the  deposits  affects  the  costs    as    follows: 
Hard  ground  and  large  boulders   require   more  power   and  there 
is    greater    loss    of   time,    one    of    the    main    factors    in    increasing 
cost.       Moreover,    the    cost    in    labor    and    repair    of    parts    is    in- 
creased. 

Clayey  ground  requires  more  disintegration  and  causes  loss 
of  gold  over  the  stacker. 

c.  Electric  power  is  the  only  form  used  in  the  districts  of 
Oroville,  Yuba,  and  Folsom,  and  is  undoubtedly  superior  to  steam, 
not  only  as  affects  reduction  of  cost,  but  on  account  of  its  advan- 
tageous application  and  control. 

d.  Climate   practically   does    not   enter   into   consideration   in 
this    region    except   as    regards    high    or    low    water    in    the    flood 
season.      Even  then  it  does  not  affect  the  cost  to  any  degree. 

No.  6.  Undoubtedly  the  most  effective  practical  system  of 
prospecting  dredging  ground  is  by  shaft.  Drilling  costs  on  the 
average  $2.50  per  foot,  and  is  often  very  unsatisfactory  in  results, 
both  as  regards  information  on  values  and  nature  of  ground.  In 
comparison  with  the  drill  as  a  method  of  sampling,  a  shaft  is 
more  thorough  and  costs  less  per  foot  above  water-level ;  even 
below  water-level,  where  pumping  is  necessary,  it  is  to  be  recom- 
mended, as  it  can  be  referred  to  afterward  in  ascertaining  the 
exact  nature  of  the  ground.  The  cost  of  shaft  sinking  by  the 
'China'  method  varies  between  90c.  and  $1.50  to  water-level,  and 
the  increase  below  this  point  varies  with  the  amount  of  water. 
These  figures  include  cost  of  panning. 

The  ratio  between  estimated  value  of  ground  by  drilling,  and 
actual  recovery  by  the  dredge,  is  not  a  fixed  proportion,  but  may 
generally  be  said  to  increase  in  constancy  over  a  large  area  roughly 
in  proportion  to  the  number  of  holes  per  acre.  Single  holes  are 
rarely  indicative  of  the  value  of  adjacent  ground,  though  a  some- 
what arbitrary  rule  that  seems  to  apply  in  practice,  is :  Where 
a  hole  gives  excessively  high  results  the  recovery  by  dredge  at 
that  spot  is  usually  lower,  and  vice  versa. 

The  care  with  which  the  computation  of  the  value  of  a  dredg- 
ing property  from  bore-holes  is  made  should  be  in  exact  propor- 


204          DREDGING   FOR    GOLD   IN   CALIFORNIA. 

tion  to  that  taken  in  computing,  by  bank  measurement  (after 
clean-up),  the  cubic  content  dredged.  The  results  are  often  viti- 
ated by  old  workings,  clay,  etc.,  encountered  by  the  drill. 

No.  7.  The  method  of  valuing  prospected  area  may  be  gener- 
ally compared  to  that  of  valuing  a  mine  from  sampling  and  assay- 
ing, except  that  in  the  former  case  the  results  are  not  so  consistent 
or  accurate.  One  authority  of  a  very  wide  experience  states  that 
before  deducting  from  the  'prospected'  value  of  the  property,  the 
cost  of  working,  interest,  depreciation,  etc.,  he  reduces  the  esti- 
mated value  as  obtained  from  drilling  by  40%.  As  I  have  already 
taken  considerable  of  your  valuable  space,  I  shall  refer  to  the 
question  of  sectionalizing  a  dredge  in  another  issue. 

In  the  criticism  of  Mr.  Curie's  article  by  C.  W.  Purington, 
appearing  in  your  issue  of  July  28,  there  are  also  several  points 
touched  upon  which,  in  my  opinion,  may  be  themselves  criticized. 
The  generalization  that  "flood  plains  reduced  nearly  to  base  level, 
in  which  streams  meander  are  *  *  *  the  first  requisite  for 
gravels  fit  for  dredging"  is  disproved  by  the  conditions  in  the 
Sacramento  valley.  Neither  the  territory  on  the  Yuba  where  the 
river  bottom,  with  its  accumulation  of  tailing  overburden,  forms 
the  gold-bearing  material,  nor  the  bench  gravels  of  the  American 
river  at  Folsom,  together  forming  probably  half  (in  value)  of  the 
available  fields,  come  under  this  head. 

The  large  dredging  area  adjacent  to  the  American  river, 
near  Folsom,  seems  to  be  almost  ignored  by  both  Mr.  Curie  and 
Mr.  Purington,  though  undoubtedly  excellent  and  remunerative 
work  is  being  done  there  today. 

Referring  to  Mr.  Purington's  criticism  of  question  No.  4, 
I  do  not  understand  Mr.  Curie's  question  to  refer  to  every  dredge 
that  has  'ever  been  built,  as  naturally  a  dredge's  life  is  only  that 
of  the  hull,  and  under  early  conditions  this  did  not  last  very  long. 
As  far  as  his  remarks  refer  to  the  districts  of  Oroville,  Yuba,  and 
Folsom,  they  seem  rather  extravagant. 

Mr.  Purington  states  that  probably  not  over  100  dredges  are 
working  at  a  profit  in  the  world.  As  there  are  probably  forty-eight 
working  at  a  profit  in  California,  and  I  am  credibly  informed  of  at 
least  four  others  in  the  United  States,  the  New  Zealand  practice, 
where  there  are  over  200  in  use,  must  be  a  losing  business. 


APPENDIX.  205 

Contrary  to  the  opinion  expressed,  I  contend  that  shaft  sink- 
ing is  feasible  in  the  large  majority  of  cases,  and  is  much  cheaper 
than  drilling.  Even  where  water  is  encountered  the  cost  in 
90%  of  cases  is  not  increased  in  indue  proportion  to  results. 
The  question  of  valuation  is  one  that  Mr.  Purington  covers  con- 
siderable space  in  treating,  but  the  sum  of  his  remarks  seems  to 
be  that  "to  enquirers  like  Mr.  Curie,"  at  least,  no  proper  system 
of  valuing  the  ground  to  show  net  profits  has  been  discovered. 
I  confess  that  I  cannot  see  any  particular  difficulties  in  computing 
the  purchasable  value  (which,  by  the  way,  is  the  real  test),  of  a 
properly  examined  and  prospected  dredging  area  other  than  those 
that  occur  in  mine  valuation.  The  increased  risk  incurred  in 
prospecting  dredging  ground  is  offset  by  the  possibility  of  change 
in  the  nature  of  orebodies  with  depth,  and  of  necessitating  differ- 
ent and  more  expensive  treatment  at  surface.  No  competent  en- 
gineer would  value  any  property,  either  dredging  or  lode,  without 
making  similar  and  proper  allowances  for  all  expenses,  including 
preliminary  and  amortization,  etc.,  and  therefore  I  do  not  see  why 
exceptional  stress  should  be  laid  on  those  points  when  applied 
to  dredging. 

D'ARCY    WEATHERBE. 
Bisbee,  October  22,  1906. 


From  MINING  AND  SCIENTIFIC  PRESS,  November  3,   1906. 


206          DREDGING   FOR    GOLD   IN   CALIFORNIA. 

Sectional  Gold  Dredges. 
The  Editor : 

Sir — Continuing  the  discussion  of  Mr.  Curie's  article,  I  de- 
sire to  say  that  the  question  of  sectionalizing  a  dredge  for  mule 
transport  over  such  rough  country  as  the  Andes  is  interesting, 
and  there  is  no  doubt  that  this  may  be  accomplished,  provided 
timber  for  the  hull  and  spuds  is  available  on  the  east  side  of 
the  range,  where  a  wider  road  than  a  bridle-path  could  be  built. 
As  to  dividing  it  up  in  eight  pieces,  that  is  of  course  out  of  the 
question,  because  the  machinery  alone  for  a  3^-cu.  ft.  bucket 
dredge  would  weigh  in  the  neighborhood  of  160  tons,  exclusive 
of  motive-power  machinery.  One-eighth  of  this  weight  is  twenty 
tons,  and  two  mules,  under  such  circumstances  as  stated,  could 
not  possibly  take  a  load  of  more  than  about  600  pounds. 

The  following  particulars  of  an  interesting  case  of  a  dredge 
being  sectionalized  for  a  property  on  the  Gold  Coast  are  given 
me  by  Mr.  C.  Cline,  formerly  connected  with  the  Risclon  Iron 
Works :  An  English  company,  known  as  the  Goldfields  of  East- 
ern Akim,  about  the  year  1900,  gave  an  order  to  the  Risdon  Iron 
Works,  of  San  Francisco,  to  build  a  dredge  for.  transportation 
from  a  point  near  Accra,  on  the  coast  of  Ashanti,  to  a  point 
sortie  sixty  miles  inland,  where  an  alleged  dredging  tract  was  situ- 
ated. The  native  method,  of  carrying  the  load  on  the  head,  was 
to  be  used,  and,  as  a  good  porter  will  only  take  about  200  Ib. 
in  this  manner,  it  will  be  readily  understood  that  the  parts  had 
necessarily  to  be  light.  Of  course,  many  pieces  could  be  slung 
between  several  natives".  It  is  related  that  a  case  is  on  record 
of  a  gigantic  native  from  the  Sahara  carrying  400  Ib.  in  this 
manner. 

It  was  intended  to  construct  the  hull  on  the  ground,  from 
native  timber,  so  the  question  of  lumber  was  eliminated.  The 
tumblers  were  built  in  twenty-five  to  thirty  pieces  each,  and  as  the 
upper  one  weighed  4000  Ib.,  this  made  the  heaviest  part  not  over  200 
Ib.  The  ladders,  trommels,  buckets,  etc.,  were  naturally  all  easy  to 
sectionalize.  As  the  dredge  was  to  be  run  by  steam,  a  boiler 
was  necessary,  and  the  intention  was  to  transport  the  plates 
separately,  the  riveting  to  be  done  on  the  ground.  The  heaviest 
single  pieces  were  the  engine  cylinders,  which  weighed  about  1000 


APPENDIX.  207 

Ib.  each.  The  tumbler  castings,  instead  of  being  pressed  onto 
the  shaft  by  hydraulic  press,  were  to  be  heated,  the  expansion 
being  sufficiently  great  to  give  a  tight  fit  when  cold.  At  the  last 
moment,  when  all  was  ready,  orders  were  received  by  cable  to 
rivet  all  sections  together  and  ship  as  an  ordinary  dredge.  This 
was  done  and  the  machinery  was  dumped  on  the  beach  at  Accra. 
Internal  trouble  had  arisen  in  the  company  meanwhile,  and  there 
was  a  stop  to  further  progress.  Some  of  the  dissentient  mem- 
bers formed  a  new  company  and  ordered  a  complete  dredge  from 
the  Risclon  company,  which  it  was  proposed  to  transport  by 
means  of  traction  engines.  This  machine  was  also  built  of  3*/2- 
cu.  ft.  bucket  capacity.  Accordingly,  three  years  after  the  first 
dredge  had  been  shipped,  a  properly  metaled  road  was  built  into 
the  property  at  a  cost,  it  is  said,  of  £30,000.  The  work  was  elabor- 
ately done,  the  road  surface  being  actually  graveled,  though  the 
native  carriers  unfortunately  avoided  this  and  took  to  the  old 
trail,  preferring  it  because  the  gravel  hurt  their  bare  feet.  Three 
traction  engines — each  of  different  design  and  of  uninterchange- 
able  parts — were  sent  out  and  proved  to  be  a  failure.  One,  I 
believe,  only  reached  a  point  seven  miles  from  the  shore.  Mr. 
Cline  was  finally  sent  out,  and  he  transported  and  erected  the 
dredge  in  six  months.  All  circular  parts  were  cased  in  wood  and 
rolled  along  the  road.  The  boiler-drum,  to  allow  for  the  camber 
of  the  road,  was  built  up  with  wood  at  the  ends  and  also  rolled 
in.  The  timber  for  the  hull  and  framing  was  cut  and  framed 
on  the  ground,  and  the  stacker-ladder  was  built  of  wood.  The 
boiler  sections  were  riveted  and  the  16- ft.  tubes  put  in  on  the 
spot.  The  ground  to  be  dredged  was  14  ft.  deep  at  the  place  of 
building  and  Mr.  Cline  ran  the  boat  for  four  weeks  after  it 
was  erected,  but  I  have  been  unable  to  learn  of  its  subsequent 
fate.  As  the  ground  had  never  been  either  drilled  or,  in  fact, 
prospected,  I  fear  that  it  is  not  hard  to  conceive  the  outcome. 

The  parts  and  weights  for  a  3^-cu.  ft.  dredge,  as  usually 
provided,  are  given  in  the  following  table,  with  the  corresponding 
number  of  sections  and  weights  into  which  each  could  be  divided. 
The  ground,  however,  to  be  worked  by  such  a  machine  far  away 
from  proper  repair  facilities,  etc.,  would  require  to  be  extremely 
rich  to  allow  the  feat  to  be  undertaken,  and  it  is  doubtful  even 
then  whether  it  would  prove  practicable. 


208 


DREDGING   FOR    GOLD   IN   CALIFORNIA. 


The   following  table*   will   give   an   idea   of   the   weight   of   a 
3^2-cu.  ft.  Bucyrus  dredge  and  the  divisibility  of  its  parts : 

Name    of    Part.  Number  of  pieces  and  their  weight. 

Can  be   cut  in  20  pieces,  one  of 

Upper   tumbler    6500      which   will   weigh    1000   lb.,   the    rest 

will  be  below  300  lb. 

Can  be  cut  in  13  pieces,  three  of 

Lower  tumbler    4500       which    will    be    about    700    lb.,    the 

rest  below  300  lb. 

Digging  ladder   28,000  Two   pieces    of   600   lb.,   the   rest 

about  300  lb. 

Digging  buckets  (Zy2  ft.)  ...  .83,000          Bottom  about  320  lb.,  each  hood 

135  lb.,  Ho  120  lb. 

Eight  pieces  would  weigh  about 

Screen,  stacker,  and  parts.  ..  16,000       60Q  lb.  each,  all  other  parts  350  lb. 

and  less;  70%  less  than  300  lb. 

Eight    parts    would   weigh    about 
Gearing     30,000      700   lb    each>   the   rest   from   350  lb. 

down;  50%  less  than  300  lb. 

Two    pieces    about    1000    lb. ;    two 
Engine  or  motors 15,000      pieces    about    600   ib.;    50%    below 

350  lb. 

Boilers    8500          All  below  350  ID. 

Pumps    300          Two    pieces    60u    lb.      All    other 

Winches    42,000      parts  below  359  ib. 

Other  parts 7600          All  below  350  lb. 


Bisbee,  November  3,  1906. 


D'ARCY  WEATHERBE. 


*  Which   I   owe  to  the   courtesy   of   D.    P.    Cameron,   of  the   Western    Engineering   & 
Construction    Co.,    of    San    Francisco,    California. 

From  MINING  AND  SCIENTIFIC  PRESS,  November  17,  1906. 


APPENDIX. 


209 


Cost  of  Dredging. 

The  following  figures,  giving  the  actual  cost  of  dredging 
operations  on  two  boats  at  Oroville,  speak  for  themselves.  They  are 
worth  more  than  many  estimates : 


COST  OF  DREDGING. 
No.   1. 


Year.  Cu.  yd. 

1903  ! 485,016 

1904 466,262 

1905  352,826 

1906  465,207 


Total  cost. 

$38,583.54 
43,430.32 
35,699.32 
35,401.30 


Four  years    1,769,311  $153,114.48 

Using  3^2-ft.  buckets  and  in  easy  digging  ground. 


No.  2. 

1905 589,082 

1906  557,084 


59,115.10 
55,454.00 


Two   years    1,146.166  $114,569.10 

Using  5-ft.  buckets  and  in  hard  digging  ground. 


Per  cu.  yd. 

$0.07959 
0.09314 
0.10118 
0.07610 

0.08654 


0.10035 
0.09954 

0.09996 


From    MINING  AND   SCIENTIFIC   PRESS,  March  ?,  1907. 


210         DREDGING   FOR   GOLD   IN   CALIFORNIA. 

Gold  Dredging. 

The  Editor : 

Sir — In  your  issue  of  November  3,  1906,  Mr.  D'Arcy 
Weatherbe  discusses  gold  dredging,  with  special  reference  to 
Mr.  Curie's  letter  on  the  same  subject  in  the  issue  of  January 
27,  1906.  In  the  closing  portion  of  Mr.  Weatherbe's  letter, 
he  refers  to  a  letter  of  mine  of  July  28,  relating  to  the  same 
subject,  and  advances  some  criticisms  thereon. 

While  in  no  way  wishing  to  decry  the  valuable  contributions 
of  Mr.  Weatherbe  concerning  California  dredging,  I  must  admit 
that  I  fail  to  see  much  force  in  the  last  portion  of  his  letter. 
I  have  not  seen,  as  yet,  from  Mr.  Weatherbe  or  others,  a 
specific  answer  to  my  question  in  the  issue  of  July  28,  as  to  the 
cost  of  dredging.  For  the  present  I  leave  this  point  open. 

Mr.  Weatherbe  objects  to  the  "generalization"  that  flood- 
plains  are  the  proper  field  for  gold  dredging.  He  answers  my 
statement  by  an  unsupported  generalization  of  his  own  that 
"Neither  the  territory  on  the  Yuba  where  the  river  bottom,  with 
its  accumulation  of  tailing  overburden,  forms  the  gold-bearing 
material,  nor  the  bench  gravels  of  the  American  river  at  Folsom, 
together  forming  probably  half  (in  value)  of  the  available  fields, 
come  under  this  head." 

I  hope  to  support,  in  the  following,  the  view  that  both  the  areas 
referred  to  are  typical  examples  of  "flood-plains  reduced  nearly  to 
base-level."  Before  proceeding,  I  wish  to  make  the  comment  that 
notwithstanding  the  number  of  highly-trained  men  now  engaged 
in  the  examination  of  dredging  conditions,  and  in  the  prosecution 
of  the  dredging  industry,  geological  factors  have  not  been  taken 
sufficiently  into  account  in  selecting  the  ground.  I  crave  space  to 
insert  here  once  more  a  description  of  what  I  believe  to  be  the 
essential  conditions  for  a  dredgeable  territory. 

"Taking  the  country  about  Oroville,  California,  as  the  best 
example  in  the  United  States,  let  the  geological  conditions  be  con- 
sidered. To  the  north  and  east  the  erosion  of  a  vast  extent  of 
mining  country,  whose  rocks  are  penetrated  by  gold-bearing  veins, 
has  contributed  little  by  little  through  geological  ages  to  the  mass 
of  detritus  now  occupying  the  bed  of  the  Feather  river.  The  wear- 


APPENDIX.  211 

ing  down  of  mountains  (originally  very  much  higher  than  at 
present)  through  a  vast  amount  of  time,  has  caused  the  formation 
of  a  valley  of  extraordinary  width,  but  of  no  great  depth.  The 
massing  of  stream  detritus  is  also  responsible  for  a  decrease  in  the 
gradient  and  a  slowing  down  almost  to  a  topographical  equilibrium 
of  the  formerly  swift  current  of  the  river.  The  stream,  unable 
under  the  conditions  to  cut  its  way  by  virtue  of  the  material  which 
is  carried  in  suspension,  has  for  a  long  time  been  depositing  its 
load,  filling  its  wide  valley  with  sand  and  gravel,  together  with  the 
less  destructible  of  the  metallic  particles,  and  notably  gold.  Geo- 
logically speaking,  the  rate  of  deposition  of  the  river's  ma- 
terial may  be  said  to  be  on  the  increase  and  the  current  of  the 
river,  still  of  considerable  velocity,  to  be  greatly  lessening  in  swift- 
ness. Later  in  its  geological  cycle  the  Feather  river  will  doubt- 
less assume,  on  a  smaller  scale,  the  present  character  of  the  Missis- 
sippi, forming  ox-bow  curves,  cut-offs,  and  as  it  were,  losing  its 
way  among  constantly  shifting  sandbars.  The  accompanying 
residual  gold,  as  it  travels  to  a  greater  and  greater  distance  from 
its  original  source  in  the  veins  of  the  mountains,  becomes  more  and 
more  finely  divided,  even  to  microscopic  dimensions,  and  increases 
in  purity,  and  the  degree  of  evenness  with  which  the  particles  are 
distributed  in  the  gravel  becomes  a  phenomenon  of  constantly  in- 
creasing definiteness  and  importance. 

Such  a  set  of  conditions  as  that  obtaining  on  Feather  river  is 
the  exception  rather  than  the  rule  in  the  western  part  of  the 
United  States,  and  even  in  California.  The  above  explanation  has 
been  entered  into  in  order  to  present  in  some  measure  the  reason 
why,  on  the  California  river  referred  to,  the  conditions  are  not  only 
favorable  but  eminently  suited  to  gold  dredging.  It  is  hardly 
necessary  to  state  that  the  amount  of  gold  increases  in  geometrical 
ratio  the  lower  it  lies  in  a  given  bed  of  gravel.  Thus,  old  rather 
than  young  valleys  are  favorable  for  dredging. 

Additional  reasons  of  great  weight  why  geological  old  valleys 
should  be  looked  for  are  that  the  size  of  boulders  is  greatly  decreased, 
gravel  becomes  by  long  abrasion  uniform  in  size,  the  angularity  of 
the  fragments  disappears,  and  a  bed  of  pebbles,  round  and  easily 
handled,  is  the  result.  The  even  distribution  of  the  gold,  which,  as 
mentioned  above,  is  an  invariable  accompaniment  of  old  and  wide 
valleys,  is  a  point  in  favor  of  this  sort  of  mining,  looked  at  from  the 


212          DREDGING   FOR   GOLD   IN   CALIFORNIA. 

standpoint  of  a  business  enterprise.  At  the  same  time  it  is  evident 
that  the  finely  divided  state  in  which  such  gold  is  found  neces- 
sitates the  highest  skill  in  recovering  it."* 

The  above  description  was  written  before  the  Yuba  and 
American  river  areas  had  become  prominent  for  dredging.  These 
areas  are  not  different  in  geological  history  from  the  Feather  river 
dredging  area.  In  fact,  I  believe  they  would  be  classified  by  any 
geologist  as  part  of  the  same  general  base-level.  The  Yuba  river, 
12  to  16  miles  east  of  Marysville,  has  a  gradient  of  less  than  50 
feet  per  mile.  It  flows  in  extensive  gravel  and  silt-filled  plain.  The 
fact  that  25  feet  of  tailing  from  former  operations  covers  the  plain 
in  and  near  the  river-bed  is  an  incident  of  artificial  origin,  which 
has  accentuated  the  natural  base-level  conditions  previously  imposed. 
Mr.  Weatherbe  perhaps  means  that  the  gold  exists  in  the  bottom  of 
the  Yuba  river  by  virtue  of  the  tailing  that  covers  the  gravel  de- 
posited in  the  natural  way.  If  this  be  the  case,  I  admit  that  a 
special  condition  exists,  but  -aa.  it  has  no  bearing  on  the  geological 
conditions,  it  does  not  constitute  a  refutation  of  my  contention. 
On  the  other  hand,  my  understanding  has  always  been  that  the 
Yuba  gold  occurs  mostly  in  the  undisturbed  gravel  beneath  the 
tailing.  If  this  be  true,  it  is  as  surely  the  gold  of  a  flood-plain  as  is 

ofthe  Feather  river. 

deposition  of  fine  alluvial  gold  in  great  river  valleys  by 
and  periodic  inundations  may  be  called  flood-gold.  No  one 
can  say  in  what  portions  of  a  given  broad  valley  the  local  currents 
will  deposit  such  fine  gold.  The  result  must  be  that  the  flood-gold 
occurs  in  patches  distributed  irregularly  over  a  wide  area.  On  the 
Yuba  I  believe  it  is  a  coincidence  that  one  such  patch,  determined 
by  prospecting,  lies  in  the  area  crossed  by  the  present  river- 
channel.  Similar  patches  will  be  found  over  a  greater  area  than 
that  at  present  exploited. 

As  regards  depth,  wells  at  Wheatland  on  the  Bear  river,  a  part 
of  the  same  great  base  level,  went  through  150  feet  of  gravel,  clay, 
hard-pan,  sand,  and  a  further  300  feet  of  greenish  sand,  all  of 
Tertiary  or  late  Cretaceous  age,  and  it  is  fair  to  assume  the  same 
depth  in  the  Yuba:  Gold  may  exist  throughout  this  depth  in 
various  layers.  By  any  present  method  it  is  unrecoverable. 


*'The  Gold-Dredging  Fields  of  Eastern  Russia,'  by  C.  W.  Purington  and  J.  B.  Land' 
field,  Engineering  Magazine,  1901,  p.  398. 


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214         DREDGING   FOR    GOLD   IN   CALIFORNIA. 

Messrs.  Becker,  Lindgren,  and  Turner,  in  the  Smartsville  folio 
of  the  Geological  Atlas,  July,  1895,  state,  regarding  the  Yuba 
valley:  "The  present  system  of  water-courses  is  steadily  degrading 
the  older  formations  and  depositing  the  sediment  on  flood-plains 
forming  bottom-lands  of  greater  or  smaller  extent  or  alluvium." 
The  elevation  that  occurred  in  Pleistocene  time  and  which  affected 
the  American  river  area  thirty  vertical  feet  or  more,  may  have  had 
some  influence  along  the  Yuba,  and  even  the  very  moderate  grade 
of  stream  was  probably  less  than  at  present.  The  river  is  at  present 
doing  but  little  cutting,  except  in  the  way  of  removing  its  artificial 
load.  The  present  dredge-tailing  is  rapidly  removed  and  re-de- 
posited further  clown  the  stream,  when  the  current  of  the  river 
comes  in  contact  with  it.  I  witnessed  an  impressive  illustration  of 
this  cutting  away  during  a  season  of  high  water  on  the  Yuba,  in 
October,  1904.  As  far  as  the  Yuba  valley  is  concerned,  I  think  it 
would  be  difficult  to  find  a  fairer  example  of  a  flood-plained  stream 
reduced  nearly  to  base-level. 

The  area  of  bench-gravel  now  being  dredged  adjacent  to  the 
American  river  at  Folsom  offers  the  conditions  of  an  ancient  base- 
level  raised  slightly  over  30  feet  above  the  present  level  of  the 
stream  that  is  reducing  it.  The  elevation  at  Folsom  does  not  exceed 
140  feet  above  the  sea,  and  the  gradient  of  the  American  river  is 
less  than  25  feet  per  mile.  The  fact  that  the  auriferous  patch  of 
gravel,  which  is  being  dredged,  lies  in  a  low  bench,  means  in  this 
case  that  the  cycle  of  base-leveling  has  been  completed,  and  that 
the  terrane  has  undergone  a  slight  elevation,  and  is  again  being  dis- 
integrated. It  has  not  only  been  reduced  to  base-level,  but  has,  as 
it  were,  been  lifted  up  for  exhibition,  to  show  what  a  base-level  flood- 
plain  should  look  like. 

Mr.  Weatherbe  has  shown  us  that  he  knows  a  great  deal  about 
dredging  operations  in  California.  He  will,  I  am  sure,  pardon  this 
protest  from  a  geologist  who  has  endeavored  to  apply  scientific 
principles  to  the  search  for  dredging  territory,  and  he  will  recognize 
that  there  may  be  ways  of  determining  what  ground  presents  dredg- 
ing possibilities,  undreamt  of  in  his  philosophy. 

C.  W.  PURINGTON. 
London,  March  11,  1907. 


From  MINING  AND  SCIENTIFIC  PRESS,  April  27,  1907. 


INDEX. 


Page 
Accident  to  Bucket-Line  of  Yuba 

No.  2  Dredge  103 

African  Dredging 186 

Agricultural  Value  of  Dredging 

Ground  164 

Alaskan  Dredging  Field  194 

Alder  Gulch,  Montana  Dredges.  86 
Amalgamating  Machine  for 

Clean-up  on  the  Butte  and  El 

Oro  Dredges  134 

American  River  Bars  15 

Average  Value  of  Gravel  at  Oro- 

ville     174 

Belt  Conveyors   72 

Biggs  No.  1  Dredge   39 

Blue  Lead  Theory  15 

Booming    18 

Boston    and    California    Dredge 

No.  1    38 

Bucket-Lines    54,   63 

Bucket-Lips    147 

Buckets 66,  192 

Burial  of  River-Channels    14 

Burmese  Dredging 187 


Caminetti  Act   20 

Canadian  Dredging 184 

Central  Gold  Dredging  Co's.  Log 

Book     32 

Centrifugal   Pumps    81 

China  Pump   41,  172 

China  Shafts   40 

Clean-up    128 

Clean-up   Practice  on  Yuba  No. 

1     4  Dredge  130 

Clean-up  Practice  on  Legget  No. 

3  Dredge  132 

Cleaning   Mercury    136 

Cline,  C 206 

Close-Connected    Bucket-Lines    .   102 

Conrey  Placer  Mines   128 

Construction  of  Dredges   46 

Core  from  Churn  Drills 28 

Cost  of  Complete  Dredge  139 

Cost  of  Drilling  Holes  33 

Costs  of  Dredging 159,  197,  209 

Curie,  J.   H 187 

Cutting  the   Bank    90 

Debris  Commission   20 

Delancy   Tract    38 


Pag- 
Deposition  of  Gold-Bearing 

Gravels 12,  212 

Depth  of  Dredging 200 

Depth  of  Erosion  of  Veins  ....  16 
Depth  of  Gravel  Deposits  ...  10,  212 
Description  of  Dredges  at  Oro- 

ville  175 

Dipper  Dredges  84 

Dredge  Construction  46 

Dredging  Machines  46 

Drill-Hole  and  Dredge  Table  38,  39 
Dumping  of  Buckets  68 

Electric    Equipment    and    Trans- 
mission          73 

El  Oro  Tract  Records  of  Colors  .  42 
Estimates  from  Drill-Records...  38 

European  Dredging  187 

Expanded  Metal  in  Sluices   110 

Factors     Affecting     Gold-Saving 

Efficiency  of  a  Dredge  124 

Feather  River  Basalt  14 

Financial  and  Statistical  Aspects 

of  Gold  Dredging  183,  201 

Flotation  Level  124 

Folsom  26 

Folsom  Companies  180 

Folsom  Development  Co's,  No.  4 

Dredge  180 

Formation  of  Terraces,  Bars,  and 

Benches  14 

Fraser  River  Dredging 184 

Garden  Ranch  Dipper  Dredge  . .     84 

Gauntrees    52 

Gearing  for  Bucket-Line  Driving  78 
Geological  Sketch  of  California  9,  210 

Glacial  Period   12 

Gold-Saving  Apparatus   on   Fol- 
som No.  4  and  5  Dredges 123 

Gold-Saving      Efficiency      of      a 

Dredge    124 

Gravel  in  Tertiary  Rivers  10 

Grizzlies     HO 

Ground  Sluicing  > 18 

Mammon  City  Dam   21 

Hammon  and  Treat 40 

Hammon,  W.  P 25 

Head-Line   Anchorage    90 

Historical  Sketch   10 


216 


INDEX. 


Page 

Holmes,  George  L 73,  193 

Holmes'  System  of  Launders  and 

Tables     118 

Horticulture  and  Dredging 164 

Hulls  of  Dredges 46 

Hydraulic  Elevator   20 

Hydraulic   Mining    20 


Ideal  Dredging  Conditions 
Insulated  Cables   


184 
108 


Jets     of     Water     for     Emptying 
Buckets     69 

Keystone   Drill    27 

Known      Areas      of      Dredging 
Ground    184 

Ladder    on    Folsom    Dev.    Go's 

No.  5  Boat  '-.  96 

Ladder  Rollers  152 

Ladders  54 

Lava  Flows  14 

Life  of  Conveyor  Belts 154 

Life  of  Pins  on  Butte  Dredge  . .  150 

Lips  of  Buckets  145 

Loss  in  Digging  Time 141 

Loss  of  Gold  in  Dredging 127 

Lost  Time  on  Butte,  El  Oro,  and 

Lava  Beds  No.  3  Dredge 142 

Lost  Time  on  Exploration  No.  1 

Dredge  143 

Lost  Time  on  Yuba  No.  1  and 

No.  2  Dredges    144 

Marine  Idea  15 

Marion  Steam  Shovel  Co.  Buck- 
ets    147 

Marysville    25 

Matto  Grosso  Gravels  186 

Melting  Room  Practice 136 

Method  of  Extracting  Pins 151 

Mooring  Boats    83 

Motors  on  the  Gaggette  Dredge..   17o 
Motors    on    the    Boston    No.    4 
Dredge   177 

Nome  Dredging  Fields  195 

Number  of  Dredges  in  the 

World  197,  204 

Number  of  Holes  Necessary  in 

Testing  Ground    33 

Ogilvie's  Dredge 193 

Open  Bucket-Lines    102 


Page 
Oroville  Companies  and  Dredges  170 

Oroville  Dredges  Described   175 

Oroville  Gravel  Value  and  Costs 
of  Working    201 


Paddock  System  40 

Pan    16 

Pins    66,    148 

Post-Glacial    Period    14 

Prehistoric  Man   14 

Preventing  Salting 30 

Production  of  Gold   16,  196 

Prospecting  Dredging  Ground  28,  198 
Prospecting  with  Churn  Drills  .  28 
Purington,  C.  W 199,  214 


Ratio      of      Recovery      Between 

Dredging   and    Drilling    36 

Reclamation  of  Worked  Ground  165 
Repair     Shops     for     Yuba     and 

Folsom  Dredges   158 

Rhodesian  Dredging   186 

Ridgway  Conveyor-Belts   155 

Robinson,   A.   Wells    193 

Rocker   17 

Russian   Dredging    195 

Rusty   Gold    127 

Sacramento   Valley    24 

Sacramento  Valley  During  Glacial 

Epoch    12 

Salting   Drillings    31 

Saskatchewan  River  Dredging    .   184 

Save-All  Sluices   112 

Screens   and   Riffles    on   Leggett 

No.  3  Dredge 116 

Screens ;    Duty,    Cost,    and    Re- 
pairs       109 

Secondary  Concentration 14 

Sectional     Dredging     Machinery 

190,  192,  206 

Shaft-Sinking  for  Testing. ..  .40,  205 

Shafting  Sizes 63,  192 

Single-Lift   Dredges    86 

Source  of  Channel  Gold 16 

South  American  Dredging  Fields 

185,    196 

Special  Labor    162 

Spuds  93,  155 

Stackers    71 

Steps  in  Placer  Mining 16 

Tables     110 

Tables  and  Sluices  on  Biggs  No. 
2   Dredge    115 


INDEX. 


217 


Page 

Tables  and  Sluices  on  the  Penn- 
sylvania Dredge    114 

Tables  and  Sluices  on  Yuba  No. 

4     114 

Tertiary  River  Channels    10 

Theories  of  Source  of  Gold 

Tom    1° 

Traveling  Cranes    l^b 

Tumblers    57,  192 

Value    of    Ground    in   Different 
Districts     13? 


Valuing  Dredging  Ground 
Variable  Flotation  Level  . 
Volcanic  Activities  


Page 
27 

.  124 
10 


Wear  on  Buckets  145 

Weatherbe,  D'Arcy  205,  208 

Weight  of  Sectional  Dredge  ....  208 

Yuba    Bottom    178 

Yuba  Companies  177 

Yuba  Dam   22 

Yuba  River  Bars   14 


THIRTEEN     FOOT    PLACER     DREDGE 
AT  FOLSOM,  CALIFORNIA. 


The  machinery  for  three- 
fourths  of  all  the  modern 
placer  dredges  now  in  use 
in  the  United  States  and 
Alaska,  in  addition  to  all 
the  steam  shovels  used  in 
digging  the  Panama  Canal, 
has  been  furnished  by  this 
Company.  ...... 


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